Water-soluble phenylpyridazine compounds and compositions containing the same

ABSTRACT

Compounds having the formula (1):  
                 
 
wherein R 1  represents an alkyl or alkenyl group, R 2  and R 3  each independently represent a hydrogen atom or an alkyl, hydroxyalkyl, dihydroxyalkyl or alkynyl group, or R 2  and R 3  may be fused together with the adjacent nitrogen atom to form a substituted or unsubstituted, nitrogen-containing, saturated heterocyclic group, X, Y and Z each independently represent a hydrogen atom, an alkyl group, a halogen atom or the like, and n stands for an integer of from 1 to 5; and also to medicinal compositions containing them. These compounds have inhibitory activity against IL-1β production, high water solubility and good oral absorbability.

FIELD OF THE INVENTION

This invention relates to water-soluble phenylpyridazine compounds, which exhibit excellent inhibitory activity against interleukin-1β production, have high water solubility and oral absorbability, and are useful for the prevention and treatment of immune system diseases, inflammatory diseases, and ischemic diseases, for example, and also to compositions containing them as effective ingredients therein.

DESCRIPTION OF THE BACKGROUND

In many diseases, for example, rheumatism, arthritis, osteoporosis, inflammatory colitis, immune deficiency syndrome, ichorrhemia, hepatitis, nephritis, ischemic diseases, insulin-dependent diabetes mellitus, arterial sclerosis, Parkinson's disease, Alzheimer's disease, and leukemia, for example, stimulation of interleukin-1β production, an inflammatory cytokine, is observed. This interleukin-1β serves to induce synthesis of an enzyme which is considered to take part in inflammation-like collagenase and PLA2 and, when intra-articularly injected to animals, causes multiarticular damage highly resembling rheumatoid arthritis. In a healthy body, on the other hand, the activity of interleukin-1β is controlled by interleukin-1 receptor, soluble interleukin-1 receptor and interleukin-1 receptor antagonist.

From research conducted using recombinant versions of these bicactivity-inhibiting substances, anti-interleukin-1β antibodies and anti-receptor antibodies against various disease models, interleukin-1β has been found to play an important role in the body, leading to an increasing potential of substances having interleukin-1β inhibitory activity as therapeutics for such diseases.

For example, immunosuppressors and steroids, which are used for the treatment of rheumatism, have been reported to inhibit production of interleukin-1β. Among compounds currently under development, KE298, a benzoylpropionic acid compound [The Japanese Society of Inflammation (11th), 1990], for example, has been reported to exhibit inhibitory activity against interleukin-1β production although it is an immunoregulator. Inhibitory activity against interleukin-1β production is also observed on a group of compounds which are called “COX-2 selective inhibitors”, for example, nimesulide as a phenoxysulfonanilide compound (DE 2333643), T-614 as a phenoxybenzopyran compound (U.S. Pat. No. 4,954,518), and tenidap (hydroxyindole compound) as a dual inhibitor (COX-1/5-LO).

Moreover, interleukin-1β production inhibitory activity is not the primary action or effect of any of these compounds so the inhibitory activity against interleukin-1β production is less than the primary action thereof.

More recently, increased synthetic research has been conducted emphasizing inhibitory activity against interleukin-1β production. Production inhibitors can be classified into (1) a group of compounds which inhibit the transfer process of an inflammatory signal to a cell nucleus and (2) another group of compounds which inhibit the enzyme ICE that functions in the processing of a precursor of interleukin-1β. Known examples of compounds presumed to have the former action 1) include SB203580 [Japanese Language Laid-Open (Kokai) Publication (PCT) No. HEI 7-503017], FRI67653 (Eur. J. Pharm., 327, 169-175, 1997), E-5090 (EP 376288), CGP47969A (Gastroenterology, 109, 812-828, 1995), hydroxyindole derivatives (Eur. J. Med. Chem. 31, 187-198, 1996), and triarylpyrrole derivatives (WO 9705878), while known examples of compounds presumed to have the latter action 2) include VE-13,045 which is a peptide compound (Cytokine, 8(5), 377-386, 1996).

None of these compounds, however, exhibits sufficient inhibitory activity against interleukin-1β production.

On the other hand, it is known that 5,6-diphenyl-pyridazine compounds exhibit analgesic and anti-inflammatory action (Eur. J. Med. Chem., 14, 53-60, 1979). Further, 6-phenylpyridazinones have been reported to be useful as cardio-active compounds (U.S. Pat. No. 4,404,203). Nothing has been reported, however, with respect to inhibitory activity of these pyridazine compounds against interleukin-1β production.

The present inventors previously reported in WO 99/44995 that high inhibitory activity against interleukin-1β production was observed on phenylpyridazine compounds. Recently, certain phenylpyridazine compounds having inhibitory activity against interleukin-1β production have been reported (JP 7-69894 A, WO 98/41511, WO 99/10331, WO 99/10332, WO 99/25697, WO 00/50408). These reported compounds, different in chemical structure from the compounds of the present invention, however.

SUMMARY OF THE INVENTION

The compounds disclosed in WO 99/44995 exhibit strong inhibitory activity against interleukin-1β production. However, the water solubility of these compounds is so low that their formulation into pharmaceutical preparations, such as tablets, was practically impossible. In the course of a further investigation, however, the present inventors discovered that the introduction of a substituted or unsubstituted aminoalkyl group to the 4-position of 6-phenylpyridazine-3-one affords a compound useful as a preventive or therapeutic for immune system diseases, inflammatory diseases, and ischemic diseases, for example, due to its significantly improved water solubility, good oral absorbability and excellent inhibitory activity against interleukin-1β production, leading to the completion of the present invention.

Thus, in one aspect of the present invention, there is provided a phenylpyridazine compound represented by the following formula (1):

wherein:

-   -   R³ represents a substituted or unsubstituted alkyl group or a         substituted or unsubstituted alkenyl group;     -   R² and R³ each independently represents a hydrogen atom or an         alkyl, hydroxyalkyl, dihydroxyalkyl or alkynyl group, or R² and         R³ may be fused together with the adjacent nitrogen atom to form         a substituted or unsubstituted, nitrogen-containing, saturated         heterocyclic group;     -   X, Y and Z each independently represents a hydrogen or halogen         atom, a substituted or unsubstituted alkyl, alkoxy, alkylthio,         alkylsulfinyl or alkylsulfonyl group, or a substituted or         unsubstituted aryl group; and     -   n stands for a number of from 1 to 5;     -   with the proviso that R² and R³ are not hydrogen atoms or the         same C₁-C₃ alkyl groups at the same time when R¹ is a benzyl         group or a C₁-C₃ alkyl group; or a salt thereof.

In another aspect of the present invention, there is also provided a pharmaceutical composition containing the phenylpyridazine compound (1) or the salt thereof as an active ingredient.

In yet a further aspect of the present invention, there is also provided a pharmaceutical composition containing the phenylpyridazine compound (1) or the salt thereof and a pharmacologically acceptable carrier.

In still a further aspect of the present invention, there is also provided a method of using the phenylpyridazine compound (1) or the salt thereof for the production of a medicine.

In a yet further aspect of the present invention, there is also provided a method for treating of a disease caused by stimulation of interleukin-1β production, which entails administering the phenylpyridazine compound (1) or the salt thereof to a mammal in need thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of the oral absorbability of a compound according to the present invention (Example 83) and a comparative compound 3;

FIG. 2 is graphic representations of the oral absorbability of another compound according to the present invention (Example 23);

FIG. 3 is graphic representations of the oral absorbability of a further compound according to the present invention (Example 25); and

FIG. 4 is graphic representations of the oral absorbability of a still further compound according to the present invention (Example 143).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the above formula (1), the alkyl moieties in the alkyl, hydroxyalkyl, dihydroxyalkyl, alkoxy, alkylthio, alkyl-sulfinyl and alkylsulfonyl groups represent those having 1 to about 12 carbon atoms, more preferably 1 to 7 carbon atoms. These alkyl moieties may include linear, branched and cyclic alkyl groups as well as alkyl groups having cyclic structures, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclopentylmethyl and cyclohexylmethyl.

In the above formula (1), the alkyl group represented by R¹ has preferably 1 to about 12 carbon atoms, more preferably 1 to 7 carbon atoms, notably 4 to 7 carbon atoms. Illustrative of such alkyl groups are linear, branched and cyclic alkyl groups as well as alkyl groups having cyclic structures. Preferred examples can include methyl, ethyl, propyl, isobutyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclopentylmethyl and cyclohexylmethyl, with methyl, ethyl, isobutyl, cyclopropylmethyl and cyclopentylmethyl being particularly preferred.

The alkenyl group represented by R¹ preferably has 2 to about 12 carbon atoms, with 2 to 7 carbon atoms being particularly preferred. Illustrative of such alkenyl groups are linear and branched alkenyl groups, specifically vinyl, propenyl, butenyl and pentenyl.

Illustrative of group(s) which the alkyl or alkenyl group represented by R¹ may contain as substituent(s) are substituted or unsubstituted aryl groups and substituted or unsubstituted heteroaryl groups. Examples of the aryl groups include aryl groups having 6 to about 14 carbon atoms, specifically phenyl and naphthyl, with phenyl being particularly preferred. Examples of the heteroaryl groups, on the other hand, include 5- or 6-membered heteroaryl groups having 1 to 3 nitrogen atoms, specifically pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrimidyl, pyrazinyl and pyridazinyl, with pyridyl being particularly preferred.

These aryl or heteroaryl groups may contain 1 to 3 substituents such as halogen atoms, alkyl groups or alkoxy groups. Examples of the halogen atoms include fluorine, chlorine, bromine and iodine, with fluorine and chlorine being particularly preferred. These alkyl and alkoxy groups preferably have 1 to 12 carbon atoms, with 1 to 7 carbon atoms being particularly preferred.

The alkyl, hydroxyalkyl and dihydroxyalkyl groups represented by R² and R³ preferably have 1 to about 12 carbon atoms, with 1 to 7 carbon atoms being particularly preferred. These groups may preferably be linear or branched. Specific examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, dihydroxypropyl and dihydroxybutyl.

The alkynyl groups represented by R² and R³ preferably have 3 to about 12 carbon atoms, with 3 to 7 carbon atoms being particularly preferred. Illustrative is propargyl (2-propynyl).

Illustrative of the nitrogen-containing, saturated heterocyclic group which may be formed as a result of fusing R² and R³ with the adjacent nitrogen atom are 5- to 7-membered saturated heterocyclic groups, specifically pyrrolidinyl, piperidino, piperazinyl, homopiperazinyl and morpholino, with piperazinyl, piperidino and morpholino being particularly preferred.

Illustrative of group(s) which these heterocyclic groups may contain as substituent (s) are halogen atoms, alkyl groups, alkoxycarbonyl groups and aralkyl groups. Examples of the halogen atoms include fluorine, chlorine, bromine and iodine. The alkyl groups can contain 1 to about 12 carbon atoms, preferably 1 to 7 carbon atoms. Illustrative of the alkoxycarbonyl groups are C₁-C₁₂ alkyloxycarbonyl groups, with C₁-C₇ alkyloxycarbonyl groups being preferred. Illustrative of the aralkyl groups are phenyl(C₁-C₇ alkyl) groups, with benzyl being particularly preferred.

Illustrative of the halogen atoms represented by X, Y and Z are fluorine, chlorine, bromine, and iodine. The alkyl groups can contain 1 to about 12 carbon atoms, with 1 to 7 carbon atoms being particularly preferred. Among these alkyl groups, linear or branched ones are particularly preferred. Illustrative of group(s) which the alkyl group may contain as substituent(s) are halogen atoms and alkoxy groups. The alkoxy, alkylthio, alkylsulfinyl and alkylsulfonyl groups can contain 1 to about 12 carbon atoms, with 1 to 7 carbon atoms being particularly preferred. Among these alkoxy, alkylthio, alkylsulfinyl and alkylsulfonyl groups, linear or branched ones are particularly preferred. Specific examples include methoxy, ethoxy, propoxy, isopropoxy, butoxy, methylthio, ethylthio, propylthio, isopropylthio, butylthio, methylsulfinyl, ethylsulfinyl, propylsulfinyl, isopropylsulfinyl, butylsulfinyl, methyl-sulfonyl, ethylsulfonyl, propylsulfonyl, isopropylsulfonyl, and butylsulfonyl. Illustrative of the aryl group are aryl groups having 6 to about 14 carbon atoms, specifically phenyl and naphthyl, with phenyl being particularly preferred. Illustrative of group(s) which the aryl group may contain as substituent(s) are halogen atoms, alkyl groups, and alkoxy groups.

n stands for a number of from 1 to 5, with 1 to 3 being more preferred, and with 1 or 3 being particularly preferred.

When R¹ is a benzyl group or a C₂-C₃ alkyl group, R² and R³ are not hydrogen atoms or the same C₁-C₃ alkyl groups at the same time.

In the formula (1), particularly preferred as R¹ are isobutyl, cyclopropylmethyl, cyclopentylmethyl, cinnamyl, halogenocinnamyl, benzyl, halogenobenzyl, dihalogenobenzyl, and (halogenophenyl)propyl. Preferred as R²and R³ are hydrogen, C₁₋₇ alkyl, C₁₋₇ hydroxyalkyl, and propargyl. Preferred as the heterocyclic group formed by R² and R³ are piperazinyl, piperidino, pyrrolidino and morpholino, each of which may optionally be substituted by one or more C₁₋₇, alkyl or benzyl groups. Preferred as X are methyl, methoxy, methylhalo, and halogens. Preferred as Y are hydrogen and halogens. Preferred as Z is hydrogen. Preferred as n are 1 and 3.

As the salt of the compound (1) of the present invention, an acid addition salt is preferred. Examples of the acid addition salt include inorganic acid salts, such as the hydrochloride, sulfate, nitrate and phosphate, and organic acid salts, such as the methanesulfonate, maleate, fumarate, citrate and oxalate.

Further, the compound according to the present invention may exist in the form of solvates and a keto-enol tautomer. Such solvates and tautomer are encompassed by the present invention. Illustrative of solvates are those formed as a result of addition of solvents used upon production, for example, water and alcohols. No particular limitation is imposed on the solvents insofar as they do not adversely affect the inhibitory activity of the compound according to the present invention against interleukin-1β production. As a solvate, the hydrate is preferred.

No particular limitation is imposed on a process for the preparation of the water-soluble phenylpyridazine compound or the salt thereof according to the present invention, and any process, which has conventionally been used for the synthesis of pyridazine compounds, and their modifications may be used. The phenylpyridazine compound (1) according to the present invention can be prepared, for example, by the following preparation processes (a) to (d).

(a) Preparation process of compounds having the formula (1) in which n=1

wherein R⁴ represents an alkyl group, Hal represents a halogen atom, Ms represents a methanesulfonyl group, and R¹, R², R³, X, Y and Z have the same meanings as described above.

A description will hereinafter be made about the individual reaction steps.

In the steps from an acetophenone (2) to a compound (5), the acetophenone (2) and diethyl ketomalonate are heated under stirring to yield a compound (3). Hydrazine is caused to act on the compound to carry out a ring-closing reaction, and the reaction product is then treated with an alkali, for example, sodium hydroxide or the like to afford a compound (4). The compound (4) is next reacted with an alcohol such as methanol to give the compound (5).

R¹-Hal is reacted to the compound (5) in the presence of an alkali such as potassium carbonate to provide a compound (6). The compound (6) is hydrolyzed into a compound (7). After ethyl chlorocarbonate is caused to act on the compound (7) to convert it into an acid anhydride, the acid anhydride is reduced with a reducing agent such as sodium borohydride to afford a compound (8). A reaction of methanesulfonyl chloride with the compound (8) in the presence of a base such as triethylamine provides a compound (9), a key intermediate in this reaction scheme.

A reaction of a desired amine (R²(R³)NH) with the compound (9) yields the target compound (1a). It is preferred to carry out this reaction, for example, in a polar solvent such as dimethylformamide in the presence or absence of an alkali such as potassium carbonate. Incidentally, if an amino group is contained in the group R² or R³ in the amine, a reaction may be carried out using a raw material protected with an appropriate protecting group for example, an alkoxycarbonyl group, followed by the removal of the protecting group.

To obtain a compound (1a) in which R² and R³ are hydrogen atoms, potassium phthalimide is reacted with the compound (9), and the reaction product is reacted further with hydrazine or the like.

(b) Preparation process of compounds having the formula (1) in which n=3

wherein Hal, Ms, R¹, R², R³, X, Y and Z have the same meanings as defined above.

According to the preparation process (b), a carbon tetrahalide such as carbon tetrabromide is firstly reacted with the compound (8) in the presence of triphenylphosphine to obtain a halogen derivative (10), with which a malonate is then reacted in the presence of sodium hydride to yield a compound (11). An acid such as trifluoroacetic acid is reacted with the compound (11) to convert it into a dicarboxylic acid, followed by heating to yield a compound (12). Ethyl chlorocarbonate is caused to act on the compound (12) to convert it into an acid anhydride, which is then reduced with a reducing agent such as sodium borohydride to yield a compound (13). Methanesulfonyl chloride is reacted with the compound (13) in the presence of a base such as triethylamine to yield a compound (14), a key intermediate in the process according to the present invention.

A target compound (1b) can be obtained by reacting a corresponding amine (R²R³NH) with the compound (14). This reaction may preferably be conducted, for example, in the presence or absence of an alkali such as potassium carbonate in a polar solvent such as dimethylformamide. When an amino group is contained in the group R² or R³ of the amine, a reaction may be conducted using a raw material in which the amino group has been protected with an appropriate protecting group (for example, an alkoxycarbonyl group), followed by deprotection of the protecting group.

To yield a compound (1b) in which R² and R³ are both hydrogen atoms, the compound can be obtained by reacting potassium phthalimide with the compound (14) and then reacting hydrazine or the like.

(c) Preparation process of compounds having the formula (1) in which n=2

wherein M represents a metal atom, and Hal, Ms, R¹, R², R³ X, Hal, Ms, Y and Z have the same meanings as defined above.

According to the preparation process (c), a cyanide such as sodium cyanide is reacted with a halogen derivative (10) to convert it into a nitrile derivative (15), which is then hydrolyzed to yield a compound (16). From the compound (16), a target compound (1c) can be obtained via an alcohol derivative (17) and a mesyloxy derivative (18) by a similar procedure as in the preparation of compounds each of which contains three methylene groups.

(d) Preparation process of compounds having the formula (1) in which n=4 or 5

These compounds can be obtained by combining the synthesis processes (b) and (c).

The salt of the compound (1) according to the present invention can be obtained by causing an organic acid or inorganic acid to act in a manner known per se in the art.

The compound (1) according to the present invention can be isolated and purified by subjecting it to purification procedures commonly employed in organic synthesis chemistry, for example, filtration, extraction, washing, drying, concentration, recrystallization, various chromatographic procedures, and/or the like. Each intermediates can be subjected to the subsequent reaction without bothering to purify it. The compound (1) may be provided as a solvate with a solvent such as a reaction solvent or recrystallization solvent, especially as the hydrate.

The compound (1) according to the present invention is excellent in water solubility, is also good in oral absorbability and has inhibitory activity against interleukin-1β production, and therefore, is useful as a preventive or therapeutic for immune system diseases, inflammatory diseases, ischemic diseases, osteoporosis, ichoremia and the like. Examples of ischemic diseases include ischemic heart diseases, ischemic encephalopathy, ischemic nephritis, and ischemic hepatitis.

The pharmaceutical composition of the present invention contains the compound (1) or the pharmaceutically acceptable salt thereof as an active ingredient. Using the active ingredient alone or together with a pharmaceutically acceptable carrier such as a solubilizer, excipient, binder or extender, it can be formed into pharmaceutical preparation forms such as tablets, capsules, granules, powders, injections and suppositories. These pharmaceutical preparations can be produced by known methods. For example, oral preparations can be produced by suitably formulating the compound (1) or the salt in combination with solubilizers such as tragacanth gum, gum arabic, sucrose esters, lecithin, olive oil, soybean oil and PEG400; excipients such as starch, mannitol and lactose; binders such as carboxy-methylcellulose sodium and hydroxypropylcellulose; disintegrators such as crystalline cellulose and carboxy-methylcellulose calcium; lubricants such as talc and magnesium stearate; anticaking agents such as light anhydrous silicic acid. The pharmaceutical composition according to the present invention is administered orally or parenterally.

The administered dosage of the pharmaceutical composition according to the present invention varies depending on the body weight, age, sex, conditions and the like of each patient. In general, however, it is preferred to administer to an adult in an amount of about 0.01 to 1,000 mg, preferably 0.1 to 100 mg, of the present pharmaceutical composition in terms of the compound (1) per day in 1 to 3 portions.

EXAMPLES

The present invention will now be further described by reference to the following Examples. The Examples are provided solely for purposes of illustration and are not intended to be limitative.

Example 1 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one 1) Preparation of 4-(1-hydroxyethyl)-2-fluorotoluene

To an ice-cold solution of 3-fluoro-4-methylbenzaldehyde (50 mg, 0.36 mmol) in THF (0.5 mL) was added dropwise a 0.93 M solution (0.47 mL) of methylmagnesium bromide (0.44 mmol) in THF. The temperature of the reaction mixture was allowed to rise back to room temperature, at which the reaction mixture was stirred for 1 hour. Then, 2 mol/L hydrochloric acid was added, and the mixture was extracted with ethyl acetate. The extract was washed with brine and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to yield title compound as a pale yellow oil (55.8 mg, quantitative).

¹H NMR (400 MHz, CDCl₃) δ: 1.46 (3H, d, J=6.4 Hz), 2.26 (3H, d, J=1.8 Hz), 4.85 (1H, q, J=6.4 Hz), 6.99-7.06 (2H, m), 7.14 (H, dd, J=7.8, 7.8 Hz).

2) Preparation of 3′-fluoro-4′-methylacetophenone

To a solution of 4-(1-hydroxyethyl)-2-fluorotoluene (55.8 mg, 0.36 mmol) in methylene chloride (1 mL) were added molecular sieve 4A (56.0 mg) and PCC 94.0 mg (0.43 mmol), and the mixture was stirred at room temperature for 1 hour. The reaction mixture was filtered through Celite, and the filtrate was concentrated under reduced pressure. The residue was purified by column chromatography on silica gel to yield the title compound as a pale yellow oil (47.5 mg, 86.0%).

¹H NMR (400 MHz, CDCl₃) δ: 2.32 (3H, d, J=1.8 Hz), 2.56 (3H, s), 7.26 (1H, dd, J=7.6, 7.6 Hz), 7.56 (1H, dd, J=1.6, 10.4 Hz), 7.62 (1H, dd, J=1.6, 7.8 Hz).

3) Preparation of ethyl 2-ethoxycarbonyl-4-(3-fluoro-4-methylphenyl)-2-hydroxy-4-oxobutanoate

A mixture of 3′-fluoro-4′-methylacetophenone (4.92 g, 32.3 mmol) and diethyl ketomalonate (6.19 g, 35.6 mmol) was stirred at 120° C. for 48 hours. The temperature of the reaction mixture was allowed to drop back to room temperature, and the mixture was purified by column chromatography on silica gel [silica gel 100 g, chloroform/ethyl acetate (10/1)] to yield the title compound as yellow crystals (8.41 9, 79.3%).

Melting point: 68.7-69.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.30 (6H, t, J=7.1 Hz), 2.34 (3H, s), 3.78 (2H, s), 4.25 (1H, s), 4.31 (4H, q, J=7.1 Hz), 7.29 (1H, dd, J=7.6 Hz), 7.59 (1H, d, J=10.2 Hz), 7.65 (1H, dd, J=1.5, 7.8 Hz).

IR (KBr) cm⁻¹: 3485, 1740, 1684, 1253, 856, 577.

4) Preparation of 4-carboxy-6-(3-fluoro-4-methylphenyl)-2H-pyridazin-3-one

To a solution of ethyl 2-ethoxycarbonyl-4-(3-fluoro-4-methylphenyl)-2-hydroxy-4-oxobutanoate (8.41 9, 25.8 mmol) inisopropanol (100 mL) was added hydrazine monohydrate (2.84 g, 56.8 mmol), and the mixture was heated under stirring at 100 for 6 hours. Then, 2 mol/L sodium hydroxide was added, and the mixture was stirred further at the same temperature for 4 hours. The reaction mixture was ice-cooled, and concentrated hydrochloric acid was added to acidify the system. The precipitate was collected by filtration, thoroughly washed with water and dried to yield the title compound as a slightly yellow crystalline powder (5.67 g, 87.7%).

Melting point: 281.3-282.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.28 (3H, d, J=1.0 Hz), 7.41 (1H, dd, J=8.1, 8.1 Hz), 7.67-7.73 (2H, m), 8.49 (1H, s), 14.09 (1H, br).

IR (KBr) cm⁻¹: 1736, 1641, 1441, 1125, 926, 806.

5) Preparation of 6-(3-fluoro-4-methylphenyl)-4-methoxy-carbonyl-2H-pyridazin-3-one

To an ice-cold suspension of 4-carboxy-6-(3-fluoro-4-methyl-phenyl)-2H-pyridazin-3-one (5.50 g, 22.2 mmol) in methanol (100 mL) was added dropwise thionyl chloride (2.72 g, 24.4 mmol), and the mixture was stirred at 80° C. for 8 hours. The temperature of the reaction mixture was allowed to drop back to room temperature, and the solvent was distilled off under reduced pressure. Water was added to the ice-cold residue. The precipitate was collected by filtration, washed with water and dried to yield the title compound as pale yellow fine-needles (5.43 g, 92.7%).

Melting point: 206.0-207.3° C.

¹H NMR (400MHz, CDCl₃) δ: 2.33 (3H, d, J=1.7 Hz), 4.00 (3H, s), 7.29 (1H, dd, J=7.9, 7.9 Hz), 7.46-7.53 (2H, m), 8.32 (1H, s), 11.61 (1H, s).

IR (KBr) cm⁻¹: 1715, 1671, 1266, 1177; 1091, 812.

6) Preparation of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one

To a solution of 6-(3-fluoro-4-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one (5.28 g, 20.0 mmol) in N,N-dimethylformamide (40 mL)-were added potassium carbonate (5.53 g, 40.0 mmol) and isobutyl bromide (3.29 g, 24.0 mmol), and the mixture was stirred at 80° C. for 1 hour. The temperature of the reaction mixture was allowed to drop back to room temperature. A saturated aqueous solution of sodium hydrogencarbonate was added, and the mixture was extracted with ethyl acetate. The extract was washed with brine, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was purified by column chromatography on silica gel [silica gel 100 g, chloroform/methanol (100/1→50/1)) to yield the title compound as an orange oil (5.41 g, 84.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.32-2.42 (1H, m), 2.33 (3H, s), 3.98 (3H, s), 4.12 (2H, d, J=7.4 Hz), 7.28 (1H, dd, J=7.8, 7.8 Hz), 7.46 (1H, dd, J=1.6, 7.8 Hz), 7.50 (1H, dd, J=1.6, 10.7 Hz), 8.21 (1H, s).

7) Preparation of 4-carboxy-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

To a suspension of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one (5.27 g, 16.6 mmol) in methanol (50 mL) was added a 2 mol/L aqueous sodium hydroxide (50 mL), and the mixture was stirred at 60° C. for 15 minutes. The temperature of the reaction mixture was allowed to drop back to room temperature, and then, water was added. After the system was acidified with concentrated hydrochloric acid, the mixture was extracted with ethyl acetate. The extract was washed with brine, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was recrystallized from chloroform-hexane to yield the title compound as colorless fine-needles (4.73 g, 93.8%).

Melting point: 159.0-159.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.02 (6H, d, J=6.7 Hz), 2.33-2.42 (1H, m), 2.35 (3H, d, J=1.6 Hz), 4.21 (2H, d, J=7.4 Hz), 7.32 (1H, dd, J=7.8, 7.8 Hz), 7.52 (1H, dd, J=1.8, 8.0 Hz), 7.55 (1H, dd, J=1.8, 10.6 Hz), 8.63 (1H, s), 14.13 (1H, s).

IR (KBr) cm⁻¹: 2960, 1742, 1633, 1574, 1425, 1101, 820.

8) Preparation of 6-(3-fluoro-4-methylphenyl)-4-hydroxy-methyl-2-isobutyl-2H-pyridazin-3-one

To a solution of 4-carboxy-6-(3-fluoro-4-methyl-phenyl)-2-isobutyl-2H-pyridazin-3-one (4.53 g, 14.9 mmol) in THF (40 mL) was added triethylamine (1.66 g, 16.4 mmol). To the ice-cooled mixture was added dropwise a solution of ethyl chlorocarbonate (1.78 g, 16.4 mmol) in THF (5 mL), and the mixture was stirred for 30 minutes. Triethylamine hydrochloride was filtered off. A solution of sodium borohydride (564 mg, 14.9 mmol) in water (1 mL) was added to the filtrate, and then, the mixture was stirred at room temperature for 10 minutes. Thereafter, 2 mol/L hydrochloric acid was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with brine, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was purified by column chromatography on silica gel [silica gel 300 g, chloroform/methanol (100/→150/1)) to yield the title compound as a colorless crystalline powder (1.08 g, 25.0%).

Melting point: 147.3-147.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.29-2.39 (1H, m), 2.32 (3H, d, J=1.8 Hz), 3.05 (1H, t, J=6.0 Hz), 4.08 (2H, d, J=7.4 Hz), 4.71 (2H, dd, J=1.2, 6.0 Hz), 7.26 (1H, dd, J=7.8 Hz), 7.46 (1H, dd, J=7.8, 7.8 Hz), 7.50 (1H, dd, J=1.8, 10.8 Hz), 7.65 (1H, s).

IR (KBr) cm⁻¹: 3330, 1644, 1596, 1514, 1226, 1087, 824.

9) Preparation of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

To an ice-cold solution of 6-(3-fluoro-4-methyl-phenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one (1.08 g, 3.73 mmol) in methylene chloride (20 mL) were added triethylamine (491 mg, 4.85 mmol) and methanesulfonyl chloride (513 mg, 4.48 mmol), and the mixture was stirred for 1 hour. A saturated aqueous solution of sodium hydrogencarbonate was added to the reaction mixture, and then, the mixture was extracted with ethyl acetate. The extract was washed with brine and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was recrystallized from chloroform-hexane to yield the title compound as a colorless crystalline powder (964 mg, 70.4%).

Melting point: 142.7-143.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.30-2.34 (1H, m), 2.33 (3H, d, J=1.8 Hz), 3.17 (3H, s), 4.08 (2H, d, J=7.4 Hz), 5.27 (2H, d, J=1.4 Hz), 7.27 (1H, dd, J=7.8, 7.8 Hz), 7.45 (1H, dd, J=1.8, 8.0 Hz), 7.50 (1H, dd, J=1.8, 10.9 Hz), 7.76 (1H, t, J=1.4 Hz).

IR (KBr) cm⁻¹: 3435, 2964, 1658, 1610, 1354, 1165, 875.

10) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

To a solution of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methanesulfonyloxy methyl-2H-pyridazin-3-one (100 mg, 0.27 mmol) in acetonitrile (1 mL) were added potassium carbonate (56.3 mg, 0.41 mmol) and tert-butyl 1-piperazine-carboxylate (60.7 mg, 0.33 mmol), and the mixture was stirred at 80° C. for 2 hours. The temperature of the reaction mixture was allowed to drop back to room temperature, and then, water was added. The mixture was extracted with chloroform. The extract was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was purified by column chromatography on silica gel [chloroform/methanol (40/1)) to yield the title compound as a yellow oil (115 mg, 92.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=3.4 Hz), 1.47 (9H, s), 2.28-2.40 (1H, m), 2.33 (3H, s), 2.52 (4H, t, J=4.7 Hz), 3.51 (4H, t, J=4.7 Hz), 3.58 (2H, s), 4.07 (2H, d, 4.1 Hz), 7.27 (1H, dd, J=7.6, 7.6 Hz), 7.44-7.52 (2H, m), 7.77 (1H, s).

Example 2 Preparation of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

To a solution of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4 -methylphenyl)-2-isobutyl-2H-pyridazin-3-one (115 mg, 0.25 mmol) in ethyl acetate (2 mL) was added a 4 mol/L solution (2 mL) of hydrochloric acid in ethyl acetate, and the mixture was stirred at 50 for 1 hour. The temperature of the reaction mixture was allowed to drop back to room temperature, and then, diethyl ether was added. The precipitate was collected to yield the title compound as a colorless crystalline powder (81.1 mg, 75.0%).

Melting point: 186.2-195.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.22-2.33 (1H, m), 2.29 (3H, d, J=2.0 Hz), 3.15 (4H, br), 3.32 (4H, t, J=5.2 Hz), 3.93 (2H, s), 4.02 (2H, d, J=7.1 Hz), 7.40 (1H, dd, J=8.1, 8.1 Hz), 7.59-7.66 (2H, m), 8.21 (1H, s).

IR (KBr) cm⁻¹: 1656, 1610, 1425, 1306, 956.

Mass m/z: 358(M⁺)

Example 3 Preparation of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1(10), 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 93.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.28-2.40 (1H, m), 2.33 (6H, s), 2.52 (4H, br), 2.62 (4H, br), 3.58 (2H, s), 4.07 (2H, d, J=7.4 Hz), 7.27 (1H, dd, J=7.9, 7.9Hz), 7.46-7.52 (2H, m), 7.75 (1H, d, J=1.0 Hz).

Example 4 Preparation of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

To a solution of 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one (94.4 mg, 0:25 mmol) in methanol (1 mL) was added dropwise at room temperature under stirring a 4 mol/L solution (0.15 mL) of hydrochloric acid in ethyl acetate. The solvent was distilled off under reduced pressure. The residue was recrystallized from methanol-diethyl ether to yield the title compound as a colorless crystalline powder (71.9 mg, 63.7%).

Melting point: 248.5-252.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.29 (3H, d, J=1.8 Hz), 2.22-2.33 (1H, m), 2.77 (3H, s), 3.18 (4H, br), 3.38 (4H, br), 3.91 (2H, s), 4.02 (2H, d, J=7.0 Hz), 7.40 (1H, dd, J=8.0, 8.0 Hz), 7.59-7.65 (2H, m), 8.16 (1H, s).

IR (KBr) cm⁻¹: 1653, 1609, 1451, 1425, 951.

Mass m/z: 372 (M⁺)

Example 5 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 84.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.96 (6H, d, J=6.6 Hz), 2.27-2.38 (1H, m), 2.30 (3H, s), 2.70 (4H, t, J=5.0 Hz), 3.66 (4H, t, J=5.2 Hz), 3.69 (2H, s), 4.06 (2H, d, J=7.2 Hz), 7.23 (1H, dd, J=7.9, 7.9 Hz), 7.46-7.52 (2H, m), 7.79 (1H, s).

Example 6 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 85.9%).

Melting point: 159.7-160.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.20-2.34 (1H, m), 2.30 (3H, d, J=1.7 Hz), 3.35 (4H, t, J=5.1 Hz), 3.84 (4H, t, J=5.1 Hz), 4.05 (2H, d, J=7.0 Hz), 4.45 (2H, s), 7.42 (1H, dd, J=8.2, 8.2 Hz), 7.62-7.68 (2H, m), 8.47 (1H, s).

IR (KBr) cm⁻¹: 1663, 1613, 1427, 1087, 1052, 821.

Mass m/z: 359 (M⁺—H₂O)

Example 7 Preparation of 4-dimethylaminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

To 6-(3-fluoro-4-methylphenyl)-2-isobutyl-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one (100 mg, 0.27 mmol) was added a 40% aqueous dimethylamine (1 mL), and the mixture was stirred at 80° C. for 2 hours. The temperature of the reaction mixture was allowed to drop back to room temperature, and then, water was added. The mixture was extracted with chloroform. The extract was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was purified by column chromatography on silica gel [chloroform/methanol (40/1)] to yield the title compound as a yellow oil (69.7 mg, 80.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.23-2.41 (1H ,m), 2.31 (3H, s), 2.35 (6H, s), 3.50 (2H, d, J=1.2 Hz), 4.08 (2H, d, J=7.4 Hz), 7.26 (1H, dd, J=7.9, 7.9 Hz), 7.47-7.54 (2H, m), 7.76 (1H, d, J=1.4 Hz).

Example 8 Preparation of 4-dimethylaminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-6-(3-fluoro-4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 85.4%).

Melting point: 246.5-248.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.23-2.34 (1H, m), 2.30 (3H, s), 2.81 (6H, s), 4.05 (2H, d, J=7.0 Hz), 4.27 (2H, s), 7.41 (1H, dd, J=8.0, 8.0 Hz), 7.22-7.68 (2H, m), 8.52 (1H, s).

IR (KBr) cm⁻¹: 1648, 1607, 1422, 1227, 1110, 1051.

Mass m/z: 317 (M⁺)

Example 9 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one 1) Preparation of 4-carboxy-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-cyclo-propylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methoxy-carbonyl-2H-pyridazin-3-one was reacted to yield the title compound as yellow crystals (yield: 98.9%).

Melting point: 169.1-170.7° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.50-0.67 (4H, m ), 1.40-1.50 (1H, m), 3.97 (3H, s), 4.23 (2H, d, J=7.3 Hz), 7.07 (1H, dd, J=8.5, 8.5 Hz), 7.57 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.85 (1H, dd, J=2.2, 12.2 Hz), 8.63 (1H, s), 14.20 (1H, s).

IR (KBr) cm⁻¹: 1761, 1629, 1521, 1476, 1461.

Mass m/z: 318 (M⁺).

2) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow fine-needles (yield: 21.3%).

Melting point: 119.4-122.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.60 (4H, m), 1.36-1.47 (1H, m), 3.12 (1H, t, J=6.0 Hz), 3.95 (3H, s), 4.10 (2H, d, J=7.3 Hz), 4.72 (2H, dd, J=1.2, 5.9 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.51 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.62 (1H, dd, J=2.2, 12.4 Hz), 7.65 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3431. 1652, 1604, 1524.

Mass m/z: 304 (M⁺).

3) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl) -4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 80.4%).

Melting point: 156.9-158.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.61 (4H, m), 1.36-1.46 (1H, m), 3.18 (3H, s), 3.95 (3H, s), 4.10 (2H, d, J=7.3 Hz), 5.28 (2H, d, J=1.2 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.51 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.62 (1H, dd, J=2.2, 12.2 Hz), 7.76 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 1656, 1612, 1523, 1358, 1177.

Mass m/z: 382 (M⁺).

4) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methylaminomethyl-2H-pyridazin-3-one

A solution of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one (160 mg, 0.42 mmol) in 30% methylamine/ethanol (5 mL) was stirred at 80° C. for 4 hours in a sealed tube. The solvent was distilled off under reduced pressure, and the residue was purified by preparative thin-layer chromatography on silica gel [developing solvent: chloroform/methanol (10/1)] to yield title compound as a slightly yellow oil (87 mg, 65.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.36-1.47 (1H, m), 1.85 (1H, br), 2.52 (3H, s), 3.80 (2H, d, J=1.2 Hz), 3.95 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.52 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.62 (1H, dd, J=2.2, 12.4 Hz), 7.66 (1H, t, J=1.2 Hz).

Mass m/z: 317 (M⁺).

Example 10 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methylaminomethyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-methylaminomethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 93.8%).

Melting point: 220.8-224.3° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.44-0.54 (4H, m), 1.29-1.40 (1H, m), 2.66 (3H, s), 3.91 (3H, s), 4.05 (2H, d, J=7.3 Hz), 4.12 (2H, s), 7.33 (1H, dd, J=8.5, 8.5 Hz), 7.70-7.79 (2H, m), 8.39 (1H, s).

IR (KBr) cm⁻¹: 1645, 1599, 1521, 1437.

Example 11 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 73.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.36-1.47 (1H, m), 2.33 (3H, s), 2.52 (4H, br), 2.62 (4H, br), 3.80 (2H, d, J=1.2 Hz), 3.58 (2H, d, J=1.0 Hz), 3.95 (3H, s), 4.09 (2H, d, J=7.3 Hz), 7.049 (H, dd, J=8.5, 8.5 Hz), 7.53 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.61 (1H, dd, J=2.2, 12.4 Hz), 7.74 (1H, t, J=1.2 Hz).

IR (Neat) cm⁻¹: 1652, 1608, 1520, 1456, 1440.

Mass m/z: 386 (M⁺).

Example 12 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (yield: 81.0%).

Melting point: 237.4-238.4° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.47-0.58 (4H, m), 1.31-1.41 (1H, m), 2.33 (3H, s), 2.52 (4H, br), 2.62 (4H, br), 2.90-3.85 (10H, m), 3.91 (3H, s), 4.03 (2H, d, J=7.3 Hz), 7.30 (1H, dd, J=8.5, 8.5 Hz), 7.70-7.78 (2H, m), 8.28 (1H, brs).

IR (KBr) cm⁻¹: 1653, 1608, 1523, 1438.

Example 13 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 88.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.37-1.48 (1H, m), 2.36 (6H, s), 3.51 (2H, s), 3.95 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.53-7.57 (1H, m), 7.64 (1H, dd, J=2.2, 12.7 Hz), 7.75 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1523, 1456, 1438.

Mass m/z: 331 (M⁺).

Example 14 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 89.0%).

Melting point: 233.6-235.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.41-0.54 (4H, m), 1.27-1.37 (1H, m), 2.83 (6H, s), 3.92 (3H, s), 4.06 (2H, d, J=7.3 Hz), 4.30 (2H, s), 7.33 (1H, dd, J=8.8, 8.8 Hz), 7.69-7.77 (2H, m), 8.51 (1H, s).

IR (KBr) cm⁻¹: 1648, 1584, 1522, 1439.

Example 15 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-N-(2-hydroxyethyl)aminomethyl-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 2-aminoethanol were reacted to yield the title compound as a yellow oil (yield: 72.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.59 (4H, m), 1.36-1.47 (1H, m), 2.86 (2H, t, J=5.1 Hz), 3.73 (2H, t, J=5.1 Hz), 3.84 (2H, d, J=1.0 Hz), 3.94 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.50-7.54 (1H, m), 7.62 (1H, dd, J=2.2, 12.7 Hz), 7.67 (1H, s).

IR (Neat) cm⁻¹: 3411, 1651, 1605, 1523, 1439.

Mass m/z: 347 (M⁺).

Example 16 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-N-(2-hydroxyethyl)aminomethyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-N-(2-hydroxyethyl)-aminomethyl-2H-pyridazin-3-one was reacted to yield the title compound as pale brown needles (yield: 79.2%).

Melting point: 166.8-169.3° C. (dec.)

¹H NMR (400 MHz, CDCl₃) δ: 0.40-0.54 (4H, m), 1.27-1;37 (1H, m), 3.13 (2H, br), 3.28 (2H, br), 3.74 (3H, s), 4.05 (2H, d, J=7.1 Hz), 4.18 (2H, s), 5.31 (1H, br), 7.33 (1H, dd, J=8.8, 8.8 Hz), 7.69-7.79 (2H, m), 8.40 (1H, s).

IR (KBr) cm⁻¹: 3334, 1654, 1616, 1604, 1523, 1441.

Example 17 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one and 1-benzylpiperazine were reacted to yield the title compound as a yellow oil (yield: 97.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.58 (4H, m), 1.36-1.46 (1H, m), 2.56 (4H, br), 2.62 (4H, br), 3.56 (2H, s), 3.58 (2H, d, J=1.0 Hz), 3.95 (3H, s), 4.09 (2H, d, J=7.1 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.23-7.36 (5H, m), 7.50-7.55 (1H, m), 7.61 (1H, dd, J=2.2, 12.7 Hz), 7.75 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1522, 1438, 1289, 1237.

Mass m/z: 462 (M⁺).

Example 18 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 4-(4-benzyl-1-piperazinyl)methyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow prisms (yield: 85.7%)

Melting point: 253.0-257.9° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.41-0.55 (4H, m), 1.27-1.38 (1H, m), 3.06-3.49 (10H, br), 3.56 (2H, s), 3.91 (3H, s), 4.02 (2H, d, J=7.3 Hz), 4.39 (2H, brs), 7.30 (1H, dd, J=8.5, 8.5 Hz), 7.44-7.48 (3H, m), 7.59-7.64 (2H, m), 7.69-7.77 (2H, m) , 8.30 (1H, brs).

IR (KBr) cm⁻¹: 1656, 1616, 1523, 1439, 1292, 1271.

Example 19 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a pale brown oil (yield: 98.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.59 (4H, m), 1.47 (9H, s), 1.38-1.46 (1H, m), 2.53 (4H, t, J=4.9 Hz), 3.51 (4H, t, J=4.9 Hz), 3.58 (2H, d, J=1.2 Hz), 3.95 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.51 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.61 (1H, dd, J=2.2, 12.7 Hz), 7.76 (1H, s).

IR (Neat) cm⁻¹: 1698, 1653, 1609, 1523, 1438, 1427.

Mass m/z: 472 (M⁺).

Example 20 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

4-(4-tert-Butoxycarbonyl-1-piperazinyl)methyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazine-3-one (220 mg, 0.47 mmol) was dissolved in ice-cold trifluoroacetic acid (2 mL), and at the same temperature, the mixture was stirred for 15 minutes. Water (10 mL) was added to the reaction mixture. The mixture was alkalinized with potassium carbonate and extracted twice with chloroform (20 mL) The extracts were washed with brine (20 mL) and dried over anhydrous sodium sulfate. The solvent was distilled off. The residue was recrystallized from chloroform-hexane to yield the title compound as pale yellow prisms (120 mg, 69.2%).

Melting point: 111.5-118.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.36-1.47 (1H, m), 2.55 (4H, br), 2.96 (4H, t, J=4.9 Hz), 3.56 (2H, d, J=1.5 Hz), 3.95 (3H, s), 4.09 (2H, d, J=7.3 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.53 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.62 (1H, dd, J=2.2, 12.7 Hz), 7.76 (1H, t, J=1.5 Hz).

IR (KBr) cm⁻¹: 3328, 1648, 1605, 1520, 1437.

Mass m/z: 372 (M⁺).

Example 21 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)-methyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow prisms (yield: 94.5%).

Melting point: 139.1-142.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.42-0.56 (4H, m), 1.29-1.39 (1H, m), 3.40 (4H, br), 3.70 (4H, br), 3.91 (3H, s), 4.16 (2H, d, J=7.3 Hz), 4.16 (2H, brs), 7.31 (1H, dd, J=8.5, 8.5 Hz), 7.71-7.73 (2H, m), 8.41 (1H, brs).

IR (KBr) cm⁻¹: 3435, 1660, 1610, 1526, 1440, 1291.

Example 22 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a pale brown oil (yield: 83.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.43-0.58 (4H, m), 1.35-1.46 (1H, m), 2.71 (4H, t, J=4.9 Hz), 3.67 (4H, t, J=4.9 Hz), 3.71 (2H, s), 3.85 (2H, br), 3.94 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.51-7.56 (1H, m), 7.61 (1H, dd, J=2.2, 12.4 Hz), 7.73 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 3616, 3476, 3275, 1648, 1601, 1529.

Mass m/z: 391 (M⁺).

Example 23 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow prisms (yield: 75.9%).

Melting point: 175.2-176.8° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.42-0.55 (4H, m), 1.28-1.39 (1H, m), 3.36 (4H, br), 3.82 (4H, br), 3.92 (3H, s), 4.06 (2H, d, J=7.3 Hz), 4.49 (2H, brs), 7.33 (1H, dd, J=8.5, 8.5 Hz), 7.71-7.79 (2H, m), 8.47 (1H, brs).

IR (KBr) cm⁻¹: 3162, 1652, 1604, 1531.

Example 24 Preparation of 4-aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one 1) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-phthalimidomethyl-2H-pyridazin-3-one

To a solution of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one (220 mg, 0.57 mmol) in N,N-dimethylformamide (5 mL) was added potassium phthalimide (160 mg, 0.87 mmol), and the mixture was stirred at 80° C. for 2 hours. Water (30 mL) was added to the reaction mixture. After stirring under cooling over ice water, precipitated crystals were collected by filtration, dried in air, and recrystallized from chloroform-hexane to yield the title compound as colorless needles (202 mg, 81.0%).

Melting point: 241.7-243.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.37-1.47 (1H, m), 3.90 (3H, s), 4.10 (2H, d, J=7.1 Hz), 4.91 (2H, d, J=1.2 Hz), 6.95 (1H, dd, J=8.5, 8.5 Hz), 7.29 (1H, t, J=1.2 Hz), 7.38 (1H, ddd, J=1.2, 2.2, 8.5 Hz), 7.48 (1H, dd, J=2.2, 12.4 Hz), 7.76-7.81 (2H, m), 7.90-7.95 (2H, m).

IR (KBr) cm⁻¹: 1712, 1653, 1614, 1524.

Mass m/z: 433 (M⁺).

2) Preparation of 4-aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

To a solution of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxypheyl)-4-phthalimidomethyl-2H-pyridazin-3-one (190 mg, 0.43 mmol) in methanol (5 mL) was added hydrazine monohydrate (110 mg, 2.20 mmol), and the mixture was heated under reflux for 2 hours. Methanol was distilled off, and chloroform (20 mL) was added to the residue. The mixture was successively washed with water (10 mL) and brine (10 mL) in this order, and was then dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was purified by preparative thin-layer chromatography on silica gel [developing solvent: chloroform/10% w/v solution of methanol in ammonia (20/1)] to yield the title compound as yellow crystals (130 mg, 97.8 %)

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.59 (4H, m), 1.37-1.47 (1H, m), 1.51 (2H, br), 3.89 (2H, d, J=1.2 Hz), 3.95 (3H, s), 4.11 (2H, d, J=7.1 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.53 (1H, ddd, J=1.2, 2.4, 8.5 Hz), 7.63 (1H, dd, J=2.2, 12.7 Hz), 7.68 (1H, s).

IR (KBr) cm⁻¹: 3393, 1651, 1606, 1523, 1438, 1293.

Mass m/z: 303 (M⁺).

Example 25 Preparation of 4-aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (81.0%).

Melting point: 188.2-194.2° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.42-0.55 (4H, m), 1.29 -1.39 (1H, m), 3.92 (3H, s), 4.01 (2H, s), 4.06 (2H, d, J=7.1 Hz), 7.34 (1H, dd, J=8.5, 8.5 Hz), 7.71-7.78 (2H, m), 8.31 (1H, s).

IR (KBr) cm⁻¹: 3507, 3440, 1644, 1581, 1522, 1438.

Example 26 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-methane-sulfonyloxy-methyl-2H-pyridazin-3-one and tert-butyl 1-piperazine-carboxylate were reacted to yield the title compound as a yellow oil (yield: 94.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 1.46 (9H, s), 2.27-2.40 (1H, m), 2.52 (4H, t, J=5.2 Hz), 3.50 (4H, t, J=5.2 Hz), 3.57 (2H, s), 3.95 (3H, s), 4.06 (2H, d, J=7.4 Hz), 7.03 (1H, dd, J=8.6, 8.6 Hz), 7.51 (1H, dd, J=1.2, 8.4 Hz), 7.60 (1H, dd, J=2.2, 12.5 Hz), 7.75 (1H, s).

Example 27 Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4-methoxy-phenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 58.5%).

Melting point: 163.0-177.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.22-2.33 (1H, m), 3.17 (4H, br), 3.33 (4H, t, J=5.3 Hz), 3.92 (3H, s), 3.96 (2H, s), 4.01 (2H, d, J=7.1 Hz), 7.27 (1H, dd, J=8.9, 8.9 Hz), 7.67-7.72 (2H, m), 8.22 (1H, s).

IR (KBr) cm⁻¹: 1656, 1608, 1522, 1440, 1291, 1113.

Mass m/z: 374 (M⁺)

Example 28 Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 80.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.28-2.40 (1H, m), 2.34 (3H, s), 2.55 (4H, br), 2.63 (4H, br), 3.58 (2H, d, J=1.4 Hz), 3.95 (3H, s), 4.06 (2H, d, J=7.4 Hz), 7.04 (1H, dd, J=8.6, 8.6 Hz), 7.53 (1H, dd, J=1.2, 8.6 Hz), 7.61 (1H, dd, J=2.2, 12.5 Hz), 7.73 (1H, s).

Example 29 Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 73.3%).

Melting point: 236.9-237.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.21-2.32 (1H, m), 2.77 (3H,s), 3.14 (4H, br), 3.36 (4H, br), 3.87 (2H, s), 3.91 (3H, s), 4.00 (2H, d, J=7.1 Hz), 7.26 (1H, dd, J=8.5, 8.5 Hz), 7.66-7.71 (2H, m), 8.12 (1H, s).

IR (KBr) cm⁻¹: 1655, 1606, 1524, 1440, 1291, 1113, 1022.

Mass m/z: 388 (M⁺)

Example 30 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 87.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.96 (6H, d, J=6.8 Hz), 2.27-2.39 (1H, m), 2.71 (4H, t, J=5.0 Hz), 3.67 (4H, t, J=5.0 Hz), 3.70 (2H, s), 3.93 (3H, s), 4.07 (2H, d, J=7.4 Hz), 7.01 (1H, dd, J=8.6, 8.6 Hz), 7.53 (1H, dd, J=1.4, 8.4 Hz), 7.61 (1H, dd, J=2.2, 12.5 Hz), 7.72 (1H, s).

Example 31 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless flakes (yield: 89.0%).

Melting point: 129.8-133.1° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.23-2.34 (1H, m), 3.34 (4H, t, J=5.1 Hz), 3.83 (4H, t, J=5.2 Hz), 3.92 (3H, s), 4.03 (2H, d, J=7.0 Hz), 4.44 (2H, s), 7.29 (1H, dd, J=8.7, 8.7 Hz), 7.69-7.75 (2H, m), 8.46 (1H, s).

IR (KBr) cm⁻¹: 1652, 1601, 1525, 1440, 1277.

Mass m/z: 362 (M⁺—CH₂OH)

Example 32 Preparation of 4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-3-(fluoro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 88.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.30-2.40 (1H, m), 2.36 (6H, s), 3.50 (2H, s), 3.93 (3H, s), 4.07 (2H, d, J=7.2 Hz), 7.02 (1H, dd, J=8.6, 8.6 Hz), 7.55 (1H, d, J=8.6 Hz), 7.63 (1H, dd, J=2.1, 12.5 Hz), 7.75 (1H, s).

Example 33 Preparation of 4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 81.0%).

Melting point: 212.4-212.8° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.23-2.33 (1H, m), 2.81 (6H, s), 3.92 (3H, s), 4.04 (2H, s, J=7.1 Hz), 4.27 (2H, s), 7.29 (1H, dd, J=8.1, 8.1 Hz), 7.70-7.75 (2H, m), 8.51 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1522, 1439, 1292, 1112.

Mass m/z: 333 (M⁺)

Example 34 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one 1) Preparation of 4-methoxycarbonyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (5), 4-carboxy-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow crystals (yield: 98.9%).

Melting point: 202.5-206.2° C.

¹H NMR (400 MHz, CDCl₃) δ: 4.01 (3H, s), 7.45-7.54 (3H, m), 7.78-7.85 (2H, m), 8.38 (1H, s), 11.86 (1H, br).

IR (KBr) cm⁻¹: 1717, 1670, 1443, 1259.

Mass m/z: 230 (M⁺).

2) Preparation of 2-isobutyl-4-methoxycarbonyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 4-methoxycarbonyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 94.1%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.6 Hz), 2.33-2.44 (1H, m), 3.98 (3H, s), 4.14 (2H, d, J=7.4 Hz), 7.42-7.51 (3H, m), 7.79-7.83 (2H, m), 8.27 (1H, s).

3) Preparation of 4-carboxy-2-isobutyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-isobutyl-4-methoxycarbonyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 82.5%).

Melting point: 120.5-121.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.03 (6H, d, J=6.6 Hz), 2.34-2.45 (1H, m), 4.23 (2H, d, J=7.4 Hz), 7.49-7.54 (3H, m), 7.84-7.89 (2H, m), 8.69 (1H, s), 14.20 (1H, s).

IR (KBr) cm⁻¹: 3448, 2956, 1741, 1636, 1418, 1116.

Mass m/z: 272 (M⁺)

4) Preparation of 4-hydroxymethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-isobutyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 22.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 3.67 (1H,br), 4.08 (2H, d, J=7.4 Hz), 4.72 (2H, d, J=3.9 Hz), 7.39-7.49 (3H, m), 7.76 (1H, t, J=1.4 Hz), 7.79-7.84 (2H, m).

5) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 4-hydroxymethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 68.4%).

Melting point: 129.7° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.30-2.41 (1H, m), 3.17 (3H, s), 4.10 (2H, d, J=7.2 Hz), 5.28 (2H, d, J=1.2 Hz), 7.43-7.52 (3H, m), 7.79-7.82 (3H, m).

IR (KBr) cm⁻¹: 3442, 2963, 1658, 1611, 1355, 1165, 872.

Mass m/z: 336 (M⁺)

6) Preparation of 4-(4-tert-butoxycarbonyl-l-piperazinyl)-methyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxy-6-phenyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted in N,N-dimethylformamide as a solvent to yield the title compound as a yellow oil (yield: 83.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 1.47 (9H, s), 2.53 (4H, t, J=4.9 Hz), 3.50 (4H, t, J=4.9 Hz), 3.59 (2H, d, J=1.0 Hz), 4.09 (2H, d, J=7.2 Hz), 7.40-7.50 (3H, m), 7.80-7.84 (3H, m).

Example 35 Preparation of 2-isobutyl-6-phenyl-4-(1-piperazinyl)-methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 67.9%).

Melting point: 154.3-159.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.94 (6H, d, J=6.8 Hz), 2.20-2.32 (1H, m), 2.86 (4H, br), 3.21 (4H, br), 3.71 (2H, s), 4.01 (2H, d, J=7.2 Hz), 7.42-7.53 (3H, m), 7.84-7.89 (2H, m), 7.96 (1H, s).

IR (KBr) cm⁻¹: 1656, 1610, 1445, 694.

Mass m/z: 326 (M⁺)

Example 36 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-phenyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 77.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.30-2.40 (1H, m), 2.34 (3H, s), 2.55 (4H, br), 2.64 (4H, br), 3.59 (2H, d, J=1.4 Hz), 4.08 (2H, d, J=7.2 Hz), 7.40-7.50 (3H, m), 7.78-7.84 (3H, m).

Example 37 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-phenyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 66.3%).

Melting point: 243.8-244.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.22-2.34 (1H, m), 2.76 (3H, s), 3.01 (4H, br), 3.30 (4H, br), 3.77 (2H, s), 4.02 (2H, d, J=7.2 Hz), 7.43-7.53 (3H, m), 7.85-7.89 (2H, m), 8.02 (1H, s).

IR (KBr) cm⁻¹: 2960, 1653, 1610, 1446.

Mass m/z: 340 (M⁺)

Example 38 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-phenyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 38.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 2.79 (4H, br), 3.70 (4H, br), 3.80 (2H, s), 4.09 (2H, d, J=7.4 Hz), 7.39-7.48 (3H, m), 7.81-7.87 (3H, m).

Example 39 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl) aminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless flakes (yield: 68.4%).

Melting point: 131.6-132.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.25-2.35 (1H, m), 3.35 (4H, t, J=5.1 Hz), 3.84 (4H, t, J=5.4 Hz), 4.06 (2H, d, J=7.1 Hz), 4.47 (2H, s), 7.45-7.54 (3H, m), 7.90-7.94 (2H, m), 8.48 (1H, s).

IR (KBr) cm⁻¹: 1655, 1610, 1421, 1053.

Mass m/z: 314 (M⁺−CH₂OH)

Example 40 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-phenyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 81.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.32-2.41 (1H, m), 2.35 (6H, s), 3.51 (2H, d, J=1.2 Hz), 4.09 (2H, d, J=7.2 Hz), 7.38-7.48 (3H, m), 7.80-7.87 (3H, m).

Example 41 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-2-isobutyl-6-phenyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow flakes (yield: 71.5%).

Melting point: 221.7-222.3° C.

¹H NMR (400MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.8 Hz), 2.24-2.35 (1H, m), 2.82 (6H, s), 4.06 (2H, d, J=7.1 Hz), 4.29 (2H, s), 7.44-7.54 (3H, m), 7.90-7.94 (2H, m), 8.54 (1H, s).

IR (KBr) cm⁻¹: 1648, 1610, 1460, 1052.

Mass m/z: 285 (M⁺)

Example 42 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one 1) Preparation of 2-isobutyl-4-methoxycarbonyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 4-methoxy-carbonyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 91.6%).

Melting point: 67.0-70.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.32-2.43 (1H, m), 2.41 (3H, s), 3.98 (3H, s), 4.13 (2H, d, J=7.3 Hz), 7.28 (2H, d, J=8.3 Hz), 7.70 (2H, d, J=8.3 Hz), 8.24 (1H, s).

IR (KBr) cm⁻¹: 1718, 1663, 1605.

Mass m/z: 300 (M⁺).

2) Preparation of 4-carboxy-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-isobutyl-4-methoxycarbonyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 86.7%).

Melting point: 162.1-165.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.02 (6H, d, J=6.8 Hz), 2.34-2.44 (1H, m), 2.47 (3H, s), 4.21 (2H, d, J=7.3 Hz), 7.31 (2H, d, J=8.3 Hz), 7.75 (2H, d, J=8.3 Hz), 8.66 (1H, s), 14.26 (1H, s).

IR (KBr) cm⁻¹: 1740, 1633, 1571, 1425.

Mass m/z: 286 (M⁺).

3) Preparation of 4-hydroxymethyl-2-isobutyl-6-(4-methyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 46.0%).

Melting point: 121.9-123.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.30-2.40 (1H, m), 2.40 (3H, s), 3.22 (1H, br), 4.08 (2H, d, J=7.3 Hz), 4.71 (2H, s), 7.27 (2H, d, J=8.3 Hz), 7.77 (1H, s), 7.70 (2H, d, J=8.3 Hz).

IR (KBr) cm⁻¹: 3334, 1645, 1596, 1522.

Mass m/z: 272 (M⁺).

4) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 4-hydroxy-methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 87.4%).

Melting point: 132.0-135.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.29-2.39 (1H, m), 2.41 (3H, s), 3.17 (3H, s), 4.08 (2H, d, J=7.6 Hz), 5.27 (2H, t, J=1.5 Hz), 7.27 (2H, d, J=8.3 Hz), 7.72 (2H, d, J=8.3 Hz), 7.79 (1H, t, J=1.5 Hz).

IR (KBr) cm⁻¹: 1656, 1609, 1355, 1166.

Mass m/z: 350 (M⁺).

5) Preparation of 4-(4-benzyl-1-piperazinyl)methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and 1-benzylpiperazine were reacted to yield the title compound as a pale yellow oil (yield: 97.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.8 Hz), 2.29-2.39 (1H, m), 2.41 (3H, s), 2.55 (4H, br), 2.61 (4H, br), 3.54 (2H, s), 3.57 (2H, d, J=1.5 Hz), 4.07 (2H, d, J=7.3 Hz), 7.22-7.36 (7H, m), 7.70 (2H, d, J=8.3 Hz), 7.77 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1657, 1652, 1518, 1455.

Mass m/z: 430 (M⁺).

Example 43 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 4-(4-benzyl-l-piperazinyl)methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 91.8%).

Melting point: 253.5-260.1° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.92 (6H, d, J=6.6 Hz), 2.18-2.28 (1H, m), 2.34 (3H, s), 3.43 (10H, br), 3.99 (2H, d, J=7.3. Hz), 4.36 (2H, brs), 7.22 (2H, d, J=8.1 Hz), 7.43-7.49 (3H, m), 7.58-7.65 (2H, m), 7.78 (2H, d, J=8.1 Hz), 8.30 (1H, brs).

IR (KBr) cm⁻¹: 1660, 1617, 1452.

Example 44 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a slightly yellow oil (yield: 96.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.38-2.41 (1H, m), 2.35 (6H, s), 2.40 (3H, s), 3.50 (2H, d, J=1.5 Hz), 4.08 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.1 Hz), 7.73 (2H, d, J=8.1 Hz), 7.78 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1652, 1609, 1518, 1455.

Mass m/z: 299 (M⁺).

Example 45 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-(4-methylphenyl)-2 -H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 91.8%).

Melting point: 237.6-239.6° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.19-2.30 (1H, m), 2.37 (3H, s), 2.81 (6H, s), 4.02 (2H, d, J=7.0 Hz), 4.30 (2H, s), 7.34 (2H, d, J=8.1 Hz), 7.81 (2H, d, J=8.1 Hz), 8.46 (1H, s).

IR (KBr) cm⁻¹: 1648, 1605, 1460, 1421.

Example 46 Preparation of 4-diethylaminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and diethylamine were reacted to yield the title compound as a pale yellow oil (yield: 95.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.07 (6H, t, J=7.1 Hz), 2.30-2.42 (1H, m), 2.40 (3H, s), 2.60 (4H, q, J=77.1 Hz), 3.60 (2H, d, J=1.5 Hz), 4.08 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.1 Hz), 7.73 (2H, d, J=8.1 Hz), 7.89 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1652, 1609, 1518, 1465, 1455.

Mass m/z: 327 (M⁺).

Example 47 Preparation of 4-diethylaminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-diethyl-aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 93.8%).

Melting point: 203.9-207.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 1.27 (6H, t, J=7.2 Hz), 2.20-2.30 (1H, m), 2.37 (3H, s), 3.09-3.24 (4H, m), 4.03 (2H, d, J=7.1 Hz), 4.28 (2H, d, J=5.4 Hz), 7.34 (2H, d, J=8.1 Hz), 7.82 (1H, d, J=8.1 Hz), 8.55 (1H, s).

IR (KBr) cm⁻¹: 1652, 1610, 1523, 1481, 1468.

Example 48 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a pale yellow oil (yield: 95.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.28-2.41 (1H, m), 2.40 (3H, s), 2.71 (4H, t, J=5.0 Hz), 3.66 (4H, t, J=5.0 Hz), 3.70 (2H, s), 3.78 (2H, br), 4.09 (2H, d, J=7.6 Hz), 7.26 (2H, d, J=8.1 Hz), 7.68 (1H, s), 7.70 (2H, d, J=8.1 Hz).

IR (Neat) cm⁻¹: 3392, 1645, 1600, 1520.

Mass m/z: 341 (M⁺−H₂O).

Example 49 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 86.4%).

Melting point: 158.9-161.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.19-2.30 (1H, m), 2.37 (3H, s), 3.27-3.46 (4H, m), 3.77-3.85 (4H, m), 4.02 (2H, d, J=7.3 Hz), 4.50 (2H, brs), 5.35 (2H, br), 7.34 (2H, d, J=8.1 Hz), 7.81 (2H, d, J=8.1 Hz), 8.46 (1H, s).

IR (KBr) cm⁻¹: 3292, 1664, 1615, 1423.

Example 50 Preparation of 4-aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one 1) Preparation of 2-isobutyl-6-(4-methylphenyl)-4-phthalimidomethyl-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 98.2%).

Melting point: 221.6-223.8° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.27-2.41 (1H, m), 2.36 (3H, s), 4.08 (2H, d, J=7.3 Hz), 4.91 (2H, d, J=1.5 Hz), 7.20 (2H, d, J=8.1 Hz), 7.32 (1H, t, J=1.5 Hz), 7.56 (2H, d, J=8.1 Hz), 7.75-7.80 (2H, m), 7.89-7.94 (2H, m).

IR (KBr) cm⁻¹: 1767, 1721, 1655, 1616.

Mass m/z: 401 (M⁺).

2) Preparation of 4-aminomethyl-2-isobutyl-6-(4-methyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 24 (2), 2-isobutyl-6-(4-methylphenyl)-4-phthalimidomethyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless prisms (yield: 98.1%).

Melting point: 74.9-77.9° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.9 Hz), 1.68 (2H, br), 2.28-2.42 (1H, m), 2.40 (3H, s), 3.87 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.0 Hz), 7.69 (1H, t, J=1.5 Hz), 7.71 (2H, d, J=8.0 Hz).

IR (KBr) cm⁻¹: 3363, 3289, 1648, 1604, 1519.

Mass m/z: 271 (M⁺).

Example 51 Preparation of 4-aminomethyl-2-isobutyl-6-(4-methyl-phenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow prisms (yield: 93.1%).

Melting point: 207.4-209.4° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.19-2.30 (1H, m), 2.37 (3H, s), 4.01 (2H, d, J=7.1 Hz), 4.02 (2H, s), 7.34 (2H, d, J=8.1 Hz), 7.80 (2H, d, J=8.l Hz), 8.26 (1H, s).

IR (KBr) cm⁻¹: 1655, 1616, 1520, 1467.

Example 52 Preparation of 4-N-(1,3-dihydroxypropan-2-yl)amino-methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and 2-amino-1,3-propanediol were reacted to yield the title compound as colorless needles (yield: 83.7%).

Melting point: 134.1-135.2° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.29-2.39 (1H, m), 2.40 (3H, s), 2.60 (3H, br), 2.82-2.87 (1H, m), 3.64 (2H, dd, J=5.6, 11.2 Hz), 3.80 (2H, dd, J=4.5, 11.2 Hz), 3.86 (2H, d, J=1.0 Hz), 4.07 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.1 Hz), 7.71 (2H, d, J=8.1 Hz), 7.74 (1H, s).

IR (KBr) cm⁻¹: 3408, 3293, 1641, 1592, 1520.

Mass m/z: 345 (M⁺).

Example 53 Preparation of 4-N-(1,3-dihydroxypropan-2-yl)amino-methyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N-(1,3-dihydroxypropan-2-yl)aminomethyl-2-isobutyl-6-(4-methyl-phenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 95.7%).

Melting point: 191.2-193.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.19-2.30 (1H, m), 2.37 (3H, s), 3.29 (1H, br), 3.60-3.78 (4H, m), 4.02 (2H, d, J=7.1 Hz), 4.29 (2H, s), 5.40 (2H, brs), 7.34 (2H, d, J=8.1 Hz), 7.81 (2H, d, J=8.1 Hz), 8.38 (1H, s).

IR (KBr) cm⁻¹: 3392, 1652, 1610.

Example 54 Preparation of 2-isobutyl-4-methylaminomethyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and methylamine were reacted to yield the title compound as a slightly yellow oil (yield: 94.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 1.87 (1H, br), 2.29-2.42 (1H, m), 2.40 (3H, s), 2.50 (3H, s), 3.76 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.1 Hz), 7.67 (1H, t, J=1.2 Hz), 7.71 (2H, d, J=8.1 Hz).

IR (Neat) cm⁻¹: 3317, 1652, 1607.

Mass m/z: 285 (M⁺).

Example 55 Preparation of 2-isobutyl-4-methylaminomethyl-6-(4-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-isobutyl-4-methylaminomethyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 97.5%).

Melting point: 198.3-201.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.20-2.31 (1H, m), 2.37 (3H, s), 2.65 (3H, s), 4.02 (2H, d, J=7.3 Hz), 4.12 (2H, s), 7.34 (2H, d, J=8.1 Hz), 7.80 (2H, d, J=8.1 Hz), 8.35 (1H, s).

IR (KBr) cm⁻¹: 3085, 1652, 1612.

Example 56 Preparation of 4-N-(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-methylphenyl)-2H-pyridazin-3-one and 2-aminoethanol were reacted to yield the title compound as a slightly yellow oil (yield: 80.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.20-2.38 (3H, m), 2.39 (3H, s), 2.84 (2H, t, J=5.1 Hz), 3.72 (2H, t, J=5.1 Hz), 3.82 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 7.26 (2H, d, J=8.1 Hz), 7.68 (1H, s), 7.70 (2H, d, J=8.1 Hz).

IR (Neat) cm⁻¹: 3429, 1652, 1601, 1519.

Mass m/z: 315 (M⁺).

Example 57 Preparation of 4-N-(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N-(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 93.4%).

Melting point: 190.8-191.9° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.20-2.31 (1H, m), 2.37 (3H, s), 3.12 (2H, t, J=5.4 Hz), 3.70-3.76 (2H, m), 4.02 (2H, d, J=7.3 Hz), 4.18 (2H, s), 5.30 (1H, br), 7.34 (2H, d, J=8.3 Hz), 7.81 (2H, d, J=8.3 Hz), 8.36 (1H, s).

IR (KBr) cm⁻¹: 3491, 1652, 1611.

Example 58 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-(4-trifluoromethyl-phenyl)-2H-pyridazin-3-one 1) Preparation of ethyl 2-ethoxycarbonyl-2-hydroxy-4-(4-trifluoromethylphenyl)-4-oxo-butanoate

Following the procedure of Example 1 (3), 4′-(trifluoromethyl)acetophenone was reacted to yield the title compound as pale yellow crystals (yield: 80.8%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30 (6H, t, J=7.1 Hz), 3.85 (2H, s), 4.22 (1H, s), 4.31 (4H, q, J=7.I Hz), 7.76 (2H, d, J=8.6 Hz), 8.07 (2H, d, J=8.6 Hz).

IR (KBr) cm⁻¹: 3446, 1750, 1727, 1691.

Mass m/z: 343 (M⁺−H₂O).

2) Preparation of 4-carboxy-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (4), ethyl 2-ethoxycarbonyl-2-hydroxy-4-(4-trifluoromethylphenyl)-4-oxobutanoate was reacted to yield the title compound as a pale brown crystalline powder (yield: 91.4%).

3) Preparation of 4-methoxycarbonyl-6-(4-trifluoromethyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (5), 4-carboxy-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow crystalline powder (yield: 88.5%).

¹H NMR (400 MHz, CDCl₃) δ: 4.02 (3H, s), 7.75 (2H, d, J=8.2 Hz), 7.95 (2H, d, J=8.2 Hz), 8.39 (1H, s), 11.69 (1H, br).

IR (KBr) cm⁻¹: 3218, 3140, 3097, 1720, 1678, 1326.

Mass m/z: 298 (M⁺).

4) Preparation of 2-isobutyl-4-methoxycarbonyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 4-methoxy-carbonyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as yellow crystals (yield: 82.2%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.6 Hz), 2.32-2.43 (1H, m), 3.99 (3H, s), 4.15 (2H, d, J=7.2 Hz), 7.74 (2H, d, J=8.4 Hz), 7.93 (2H, d, J=8.4 Hz), 8.12 (1H, s).

IR (Neat) cm⁻¹: 2961, 1746, 1670, 1327, 1115, 1068.

Mass m/z: 354 (M⁺).

5) Preparation of 4-carboxy-2-isobutyl-6-(4-trifluoro-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-isobutyl-4-methoxycarbonyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 91.6%).

Melting point: 184.4-185.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.03 (6H, d, J=6.6 Hz), 2.34-2.45 (1H, m), 4.25 (2H, d, J=7.2 Hz), 7.78 (2H, d, J=8.2 Hz), 7.99 (2H, d, J=8.2 Hz), 8.70 (1H, s), 14.02 (1H, s).

IR (KBr) cm⁻¹: 3447, 1739, 1631, 1570, 1330, 1174, 1114, 1070, 847.

Mass m/z: 340 (M⁺)

6) Preparation of 4-hydroxymethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 28.1%).

Melting point: 145.8-146.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.30-2.41 (1H, m), 2.96 (1H, t, J=5.9 Hz), 4.11 (2H, d, J=7.4 Hz), 4.74 (2H, dd, J=1.4, 5.8 Hz), 7.70-7.74 (3H, m), 7.94 (2H, d, J=8.2 Hz).

IR (KBr) cm⁻¹: 3339, 1646, 1596, 1328, 1131, 1070, 848.

7) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 4-hydroxy-methyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 89.9%).

Melting Point: 122.9-123.8° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 3.18 (3H, s), 4.11 (2H, d, J=7.2 Hz), 5.29 (2H, d, J=1.4 Hz), 7.73 (2H, d, J=8.2 Hz), 7.83 (1H, t, J=1.4 Hz), 7.93 (2H, d, J=8.2 Hz).

IR (KBr) cm⁻¹: 3447, 1659, 1613, 1359, 1329, 1169, 1123, 1071, 846.

Mass m/z: 404 (M⁺)

8) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 83.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 1.47 (9H, s), 2.29-2.41 (1H, m), 2.53 (4H, t, J=4.9 Hz), 3.51 (4H, t, J=4.8 Hz), 3.60 (2H, s), 4.10 (2H, d, J=7.4 Hz), 7.72 (2H, d, J=8.2 Hz), 7.84 (1H, s), 7.94 (2H, d, J=8.2 Hz).

Example 59 Preparation of 2-isobutyl-4-(1-piperazinyl)methyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 95.0%).

Melting point: 210.8-212.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.22-2.35 (1H, m), 3.12 (4H,br), 3.30 (4H, t, J=5.2 Hz), 3.92 (2H, s), 4.05 (2H, d, J=7.1 Hz), 7.84 (2H, d, J=8.3 Hz), 8.11 (2H, d, J=8.1 Hz), 8.25 (1H, s).

IR (KBr) cm⁻¹: 1656, 1608, 1328, 1125, 1069.

Mass m/z: 394 (M⁺)

Example 60 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 81.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.30-2.41 (1H, m), 2.33 (3H, s), 2.53 (4H, br), 2.63 (4H, br), 3.60 (2H, s), 4.10 (2H, d, J=7.2 Hz), 7.72 (2H, d, J=8.2 Hz), 7.83 (1H, s), 7.94 (2H, d, J=8.2 Hz).

Example 61 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless flakes (yield: 88.6%).

Melting point: 249.9-252.8° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.22-2.35 (1H, m), 2.77 (3H, s), 3.14 (4H, br), 3.35 (4H, br), 3.88 (2H, s), 4.05 (2H, d, J=7.2 Hz), 7.84 (2H, d, J=8.2 Hz), 8.10 (2H, d, J=8.0 Hz), 8.19 (1H, s).

IR (KBr) cm⁻¹: 2966, 1653, 1610, 1328, 1125, 1069.

Mass m/z: 408 (M⁺)

Example 62 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 79.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 2.72 (4H, br), 3.67 (4H, t, J=4.2 Hz), 3.72 (2H, s), 4.10 (2H, d, J=7.4 Hz), 7.70 (2H, d, J=7.6 Hz), 7.82 (1H, s), 7.94 (2H, d, J=8.2 Hz).

Example 63 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-(4-trifluoromethyl-phenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 58.2%).

Melting point: 134.9-135.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.6 Hz), 2.25-2.36 (1H, m), 3.34 (4H, br), 3.83 (4H, t, J=5.1 Hz), 4.07 (2H, d, J=7.0 Hz), 4.46 (2H, s), 7.86 (2H, d, J=8.2 Hz), 8.13 (2H, d, J=8.2 Hz), 8.55 (1H, s).

IR (KBr) cm⁻¹: 1653, 1605, 1319, 1125, 1069.

Mass m/z: 395 (M⁺−H₂O)

Example 64 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 80.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.31-2.40 (1H, m), 2.36 (6H, s), 3.51 (2H, d, J=1.2 Hz), 4.10 (2H, d, J=7.4 Hz), 7.71 (2H, d, J=8.4 Hz), 7.83 (1H, t, J=l.4 Hz), 7.97 (2H, d, J=8.2 Hz).

Example 65 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethylaminomethyl-2-isobutyl-6-(4-trifluoromethylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow flakes (yield: 93.0%).

Melting point: 242.2-242.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.6 Hz), 2.25-2.36 (1H, m), 2.83 (6H, s), 4.07 (2H, d, J=7.3 Hz), 4.30 (2H, s), 7.86 (2H, d, J=8.3 Hz), 8.14 (2H, d, J=8.0 Hz), 8.61 (1H, s).

IR (KBr) cm⁻¹: 2963, 1646, 1606, 1321, 1115, 1069.

Mass m/z: 353 (M⁺)

Example 66 Preparation of 6-(4-biphenylyl)-4-(4-tert-butoxy-carbonyl-1-piperazinyl)methyl-2-isobutyl-2H-pyridazin-3-one 1) Preparation of ethyl 4-(4-biphenylyl)-2-ethoxycarbonyl-2-hydroxy-4-oxobutanoate

Following the procedure of Example 1 (3), 4-acetyl-biphenyl was reacted to yield the title compound as colorless flakes (yield: 83.3%).

Melting point: 88.0-88.3° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.31 (6H, t, J=7.1 Hz), 3.87 (2H, s), 4.32 (4H, q,7.1 Hz), 7.41 (1H, tt, J=1.4, 7.2 Hz), 7.48 (2H, dd, J=7.2, 7.2 Hz), 7.63 (2H, d, J=7.0 Hz), 7.70 (2H, d, J=8.6 Hz), 8.04 (2H, d, J=8.6 Hz).

IR (KBr) cm⁻¹: 3449, 1736, 1680, 1604, 1301, 1244, 1204, 763.

2) Preparation of 6-(4-biphenylyl)-4-carboxy-2H-pyridazin-3-one

Following the procedure of Example 1 (4), ethyl 4-(4-biphenylyl)-2-ethoxycarbonyl-2-hydroxy-4-oxobutanoate was reacted to yield the title compound as a yellow crystalline powder (yield: 90.2%).

Melting point: 299.7-300.8° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 7.40 (1H, t, J=7.4 Hz), 7.49 (2H, dd, J=7.4, 7.4 Hz), 7.74 (2H, d, J=7.2 Hz), 7.82 (2H, d, J=8.4 Hz), 8.03 (2H, d, J=8.4 Hz), 8.54 (1H, s).

IR (KBr) cm⁻¹: 1753, 1652, 1590, 1446, 1201, 768.

3) Preparation of 6-(4-biphenylyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (5), 6-(4-biphenylyl)-4-carboxy-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 90.4%).

Melting point: 277.0-277.9° C. (dec.)

¹H NMR (400 MHz, CDCl₃) δ: 4.01 (3H, s), 7.39-7.45 (3H, m), 7.64 (2H, d, J=7.2 Hz), 7.72 (2H, d, J=8.2 Hz), 7.89 (2H, d, J=8.0 Hz), 8.42 (1H, s), 10.7 (1H, s).

IR (KBr) cm⁻¹: 2954, 1727, 1671, 1594, 1265, 1098, 768.

4) Preparation of 6-(4-biphenylyl)-2-isobutyl-4-methoxy-carbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(4-biphenylyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as yellow crystals (yield: 62.7%).

Melting point: 186.2-195.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.01 (6H, d, J=6.8 Hz), 2.34-2.45 (1H, m), 3.99 (3H, s), 4.16 (2H, d, J=7.4 Hz), 7.39 (1H, tt, J=1.4, 7.4 Hz), 7.48 (2H, dd, J=7.2, 7.2 Hz), 7.64 (2H, d, J=7.0 Hz), 7.71 (2H, d, J=8.6 Hz), 7.89 (2H, d, J=8.6 Hz), 8.31 (1H, s).

5) Preparation of 6-(4-biphenylyl)-4-carboxy-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 6-(4-biphenylyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 79.2%).

Melting point: 156.9-157.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.04 (6H, d, J=6.6 Hz), 2.36-2.46 (1H, m)4.24 (2H, d, J=7.4 Hz), 7.41 (1H, t, J=7. 4 Hz), 7.49 (2H, dd, J=7.4, 7.4 Hz), 7.65 (2H, d, J=7.0 Hz), 7.74 (2H, d, J=8.4 Hz), 7.95 (2H, d, J=8.4 Hz), 8.73 (1H, s), 14.22 (1H, s).

IR (KBr) cm⁻¹: 2963, 1749, 1631, 1565, 1470, 735.

6) Preparation of 6-(4-biphenylyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 6-(4-biphenylyl)-4-carboxy-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a while solid (yield: 15.6%).

Melting point: 146.4-147.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.01 (6H, d, J=6.8 Hz), 2.32-2.43 (1H, m), 3.13 (1H, t, J=6.2 Hz), 4.11 (2H, d, J=7.4 Hz), 4.74 (2H, dd, J=1.2, 6.2 Hz), 7.39 (1H, t, J=7.3 Hz), 7.48 (2H, dd, J=7.4, 7.4 Hz), 7.64 (2H, d, J=7.0 Hz), 7.70 (2H, d, J=8.6 Hz), 7.74 (1H, t, J=1.2 Hz), 7.90 (2H, d, J=8.6 Hz).

IR (KBr) cm⁻¹: 3431, 2961, 1647, 1596, 1077, 769.

7) Preparation of 6-(4-biphenylyl)-2-isobutyl-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 6-(4-biphenylyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 79.3%).

Melting point: 121.3-122.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.01 (6H, d, J=6.8 Hz), 2.33-2.42 (1H, m), 3.18 (3H, s), 4.12 (2H, d, J=7.4 Hz), 5.30 (2H, d, J=1.2 Hz), 7.39 (1H, t, J=7.4 Hz), 7.48 (2H, dd, J=7.6 Hz), 7.64 (2H, d, J=7.4 Hz), 7.71 (2H, d, J=8.4 Hz), 7.85-7.91 (3H, m).

IR (KBr) cm⁻¹: 2964, 1658, 1610, 1354, 1165, 874, 529.

8) Preparation of 6-(4-biphenylyl)-4-(4-tert-butoxy-carbonyl-1-piperazinyl)methyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(4-biphenylyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-pipeazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 87.7%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.6 Hz), 1.47 (9H, s), 2.30-2.43 (1H, m), 2.54 (4H, t, J=4.9 Hz), 3.51 (4H, t, J=4.9 Hz), 3.60 (2H, d, J=1.4 Hz), 4.10 (2H, d, J=7.4 Hz), 7.38 (1H, tt, J=1.4, 7.2 Hz), 7.47 (2H, dd, J=7.4, 7.4 Hz), 7.64 (2H, d, J=7.0 Hz), 7.70 (2H, d, J=8.6 Hz), 7.85-7.92 (3H, m).

Example 67 Preparation of 6-(4-biphenylyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 6-(4-biphenylyl)-4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 51.5%).

Melting point: 226.8-228.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.8 Hz), 2.25-2.36 (1H, m), 3.19 (4H, br), 3.34 (4H, t, J=5.1 Hz), 3.98 (2H, s), 4.05 (2H, d, J=7.1 Hz), 7.39 (1H, t, J=7.3 Hz), 7.49 (2H, dd, J=7.7, 7.7 Hz), 7.71 (2H, d, J=7.8 Hz), 7.79 (2H, d, J=8.3 Hz), 7.99 (2H, d, J=8.3 Hz), 8.29 (1H, s).

IR (KBr) cm⁻¹: 1653, 1604, 1446, 771.

Mass m/z: 402 (M⁺)

Example 68 Preparation of 6-(4-biphenylyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(4-biphenylyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 68.2%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.6 Hz), 2.30-2.43 (1H, m), 2.34 (3H, s), 2.55 (4H, br), 2.65 (4H, br), 3.61 (2H, d, J=1.2 Hz), 4.10 (2H, d, J=7.2 Hz), 7.38 (1H, t, J=7.3 Hz), 7.47 (2H, dd, J=7.5, 7.5 Hz), 7.64 (2H, d, J=7.2 Hz), 7.70 (2H, d, J=8.4 Hz), 7.84 (1H, s), 7.90 (2H, d, J=8.4 Hz).

Example 69 Preparation of 6-(4-biphenylyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(4-biphenylyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 69.9%).

Melting point: 262.2-263.6° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.6 Hz), 2.26-2.35 (1H, m), 2.77 (3H, s), 3.10 (4H, br), 3.34 (4H, br), 3.85 (2H, s), 4.04 (2H, d, J=7.1 Hz), 7.39 (1H, t, J=7.6 Hz), 7.49 (2H, dd, J=8.0, 8.0 Hz), 7.71 (2H, d, J=8.0 Hz), 7.78 (2H, d, J=8.3 Hz), 7.89 (2H, d, J=8.3 Hz), 8.13 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1465, 1050.

Mass m/z: 416 (M⁺)

Example 70 Preparation of 6-(4-biphenylyl)-4-N,N-bis(2-hydroxy-ethyl)aminomethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(4-biphenylyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 62.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.30-2.43 (1H, m), 2.73 (4H, t, J=4.8 Hz), 3.67 (4H, t, J=4.8 Hz), 3.73 (2H, s), 4.12 (2H, d, J=7.4 Hz), 7.38 (1H, t, J=7.2 Hz), 7.47 (2H, dd, J=7.2, 7.2 Hz), 7.63 (2H, d, J=7.4 Hz), 7.68 (2H, d, J=8.2 Hz), 7.79 (1H, s), 7.89 (2H, d, J=8.2 Hz).

Example 71 Preparation of 6-(4-biphenylyl)-4-N,N-bis(2-hydroxy-ethyl)aminomethyl-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(4-biphenylyl)-4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 63.9%).

Melting point: 218.3-218.6° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.98 (6H, d, J=6.8 Hz), 2.26-2.37 (1H, m), 3.36 (4H, t, J=5.1 Hz), 3.85 (4H, t, J=5.1 Hz), 4.08 (2H, d, J=7.3 Hz), 4.48 (2H, s), 7.40 (1H, tt, J=1.2, 7.3 Hz), 7.49 (2H, dd, J=7.3 Hz), 7.72 (2H, dd, J=1.2, 7.3 Hz), 7.81 (2H, d, J=8.3 Hz), 8.01 (2H, d, J=8.3 Hz), 8.52 (1H, s).

IR (KBr) cm⁻¹: 1654, 1607, 1053, 847, 769.

m/z (EI): 403 (M⁺−H₂O)

Example 72 Preparation of 6-(4-biphenylyl)-4-dimethylamino-methyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(4-biphenylyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 87.7%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.6 Hz), 2.36 (6H, s), 2.29-2.43 (1H, m), 3.52 (2H, d, J=1.0 Hz), 4.10 (2H, d, J=7.2 Hz), 7.37 (1H, t, J=7.4 Hz), 7.46 (2H, dd, J=7.4, 7.4 Hz), 7.63 (2H, d, J=7.2 Hz), 7.68 (2H, d, J=8.4 Hz), 7.85 (1H, s), 7.92 (2H, d, J=8.4 Hz).

Example 73 Preparation of 6-(4-biphenylyl)-4-dimethylamino-methyl-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(4-biphenylyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless flakes (yield: 58.2%).

Melting point: 243.9-244.1° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.98 (6H, d, J=6.6 Hz), 2.26-2.37 (1H, m), 2.83 (6H, s), 4.03 (2H, d, J=7.1 Hz), 4.30 (2H, s), 7.39 (1H, tt, J=1.2, 7.3 Hz), 7.49 (2H, dd, J=7.3, 7.3 Hz), 7.72 (2H, dd, J=1.2, 7.1 Hz), 7.81 (2H, d, J=8.8 Hz), 8.02 (2H, d, J=8.6 Hz), 8.57 (1H, s).

IR (KBr) cm⁻¹: 1647, 1604, 1460, 1409, 1052.

Mass m/z: 361 (M⁺)

Example 74 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-chloro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and tert-butyl 1-piperazine-carboxylate were reacted to yield the title compound as a yellow oil (yield: 89.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.47 (9H, s), 2.27-2.40 (1H, m), 2.52 (4H, t, J=4.9 Hz), 3.50 (4H, t, J=5.0 Hz), 3.57 (2H, d, J=1.4 Hz), 3.96 (3H, s), 4.07 (2H, d, J=7.2 Hz), 7.00 (1H, d, J=8.6 Hz), 7.66 (1H, dd, J=2.4, 8.6 Hz), 7.74 (1H, t, J=1.3 Hz), 7.86 (1H, d, J=2.4 Hz).

Example 75 Preparation of 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-chloro-4-methoxy-phenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 70.2%).

Melting point: 203.6-204.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.6 Hz), 2.20-2.34 (9H, m), 3.14 (4H, br), 3.31 (4H, t, J=5.2 Hz), 3.93 (5H, s), 4.01 (2H, d, J=7.0 Hz), 7.26 (1H, d, J=8.8 Hz), 7.84 (1H, dd, J=2.4, 8.6 Hz), 7.91 (1H, d, J=2.4 Hz), 8.19 (1H, s).

IR (KBr) cm⁻¹: 1654, 1608, 1507, 1289, 1065.

Mass m/z: 390 (M⁺), 392 (M⁺).

Example 76 Preparation of 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 76.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.28-2.40 (1H, m), 2.33 (3H, s), 2.53 (4H, br), 2.63 (4H, br), 3.58 (2H, d, J=1.2 Hz), 3.96 (3H, s), 4.06 (2H, d, J=7.2 Hz), 7.01 (1H, d, J=8.6 Hz), 7.67 (1H, dd, J=2.2, 8.6 Hz), 7.72 (1H, s), 7.86 (1H, d, J=2.2 Hz).

Example 77 Preparation of 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 67.5%).

Melting point: 235.8-236.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.25-2.32 (1H, m), 2.77 (3H, s), 3.15 (4H, br), 3.36 (4H, br), 3.88 (2H, s), 3.93 (3H, s), 4.01 (2H, d, J=7.0 Hz), 7.26 (1H, d, J=8.6 Hz), 7.83 (1H, dd, J=2.2, 8.6 Hz), 7.91 (1H, d, J=2.2 Hz), 8.12 (1H, s).

IR (KBr) cm⁻¹: 1653, 1608, 1507, 1289, 1064.

Mass m/z: 404 (M⁺), 406 (M⁺).

Example 78 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-chloro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 79.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.96 (6H, d, J=6.6 Hz), 2.28-2.39 (1H, m), 2.71 (4H, t, J=4.9 Hz), 3.66 (4H, t, J=4.9 Hz), 3.70 (2H, s), 3.94 (3H, s), 4.07 (2H, d, J=7.4 Hz), 6.98 (1H, d, J=8.8 Hz), 7.68 (1H, dd, J=1.8, 8.7 Hz), 7.72 (1H, s), 7.85 (1H, d, J=2.1 Hz).

Example 79 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-chloro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-chloro-4-methoxyphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 60.1%).

Melting point: 153.0-153.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.6 Hz), 2.23-2.34 (1H, m), 3.34 (4H, t, J=5.1 Hz), 3.83 (4H, t, J=5.1 Hz), 3.94 (3H, s), 4.04 (2H, d, J=7.1 Hz), 4.44 (2H, s), 7.28 (1H, d, J=8.8 Hz), 7.85 (1H, dd, J=2.4, 8.6 Hz), 7.94 (1H, d, J=2.4 Hz), 8.45 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1508, 1421, 1293, 1062.

Mass m/z: 391 (M⁺−H₂O)

Example 80 Preparation of 6-(3-chloro-4-methoxyphenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(3-chloro-4-methoxyphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 84.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.31-2.39 (1H, m), 2.35 (6H, s), 3.50 (2H, s), 3.95 (3H, s), 4.07 (2H, d, J=7.2 Hz), 6.99 (1H, d, J=8.6 Hz), 7.70 (1H, dd, J=1.4, 8.6 Hz), 7.88 (1H, d, J=1.4 Hz).

Example 81 Preparation of 6-(3-chloro-4-methoxyphenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(3-chloro-4-methoxyphenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 69.4%).

Melting point: 213.6-214.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.22-2.34 (1H, m), 2.81 (6H, s), 3.94 (3H, s), 4.04 (2H, d, J=7.1 Hz), 4.27 (2H, s), 7.28 (1H, d, J=8.8 Hz), 7.87 (1H, dd, J=2.2, 8.8 Hz), 7.95 (1H, d, J=2.2 Hz), 8.53 (1H, s).

IR (KBr) cm⁻¹: 1652, 1608, 1508, 1289, 1064.

Mass m/z: 349 (M⁺), 351 (M⁺).

Example 82 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of ethyl 2-ethoxycarbonyl-4-(4-fluoro-3-methylphenyl)-2-hydroxy-4-oxobutanoate

Following the procedure of Example 1 (3), 5-acetyl-2-fluorotoluene was reacted to yield the title compound as pale yellow prisms (yield: 95.9%).

¹H NMR(400 MHz, CDCl₃) δ: 1.30 (6H, t, J=7.1 Hz), 2.33 (3H, d, J=1.7 Hz), 3.79 (2H, s), 4.29 (1H, s), 4.31 (4H, q, J=7.1 Hz), 7.08 (1H, dd, J=8.8, 8.8 Hz), 7.78-7.85 (2H, m).

2) Preparation of 4-carboxy-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1(4), ethyl 2-ethoxycarbonyl-4-(4-fluoro-3-methylphenyl)-2-hydroxy-4-oxo-butanoate was reacted to yield the title compound as a pale yellow crystalline powder (yield: 88.9%).

Melting point: 213.6-214.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.51 (3H, d, J=1.7 Hz), 7.26 (1H, dd, J=9.1, 9.1 Hz), 7.77-7.81 (1H, m), 7.89 (1H, d, J=7.3 Hz), 8.49 (1H, s), 13.99 (1H, br).

3) Preparation of 6-(4-fluoro-3-methylphenyl)-4-methoxy-carbonyl-2H-pyridazin-3-one

Following the procedure of Example 1(5), 4-carboxy-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 76.8%).

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=2.0 Hz), 3.99 (3H, s), 7.10 (1H, dd, J=8.9, 8.9 Hz), 7.58-7.62 (1H, m), 7.60 (1H, d, J=7.3 Hz), 8.31 (1H, s).

4) Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1(6), 6-(4-fluoro-3-methylphenyl)-2-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow prisms (yield: 86.3%).

Melting point: 71.4-73.8° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.31-2.42 (1H, m), 2.35 (3H, d, J=2.0 Hz), 3.98 (3H, s), 4.12 (2H, d, J=7.3 Hz), 7.10 (H, dd, J=8.8, 8.8 Hz), 7.57-7.65 (2H, m), 8.21 (1H, s).

5) Preparation of 4-carboxy-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1(7), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (yield: 90.0%).

Melting point: 129.3-132.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.02 (6H, d, J=6.8 Hz), 2.33-2.44 (1H, m), 2.37 (3H, d, J=2.0 Hz), 4.21 (2H, d, J=7.3 Hz), 7.13 (1H, dd, J=8.8, 8.8 Hz), 7.64-7.71 (2H, m), 8.63 (1H, s).

IR (KBr) cm⁻¹: 1742, 1636, 1537, 1422.

Mass m/z: 304 (M⁺).

6) Preparation of 6-(4-fluoro-3-methylphenyl)-4-hydroxy-methyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1(8), 4-carboxy-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 24.7%).

Melting point: 107.4-110.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99(6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 2.35 (3H, d, J=1.7 Hz), 3.14 (1H, t, J=5.9 Hz), 4.08 (2H, d, J=7.6 Hz), 4.71 (2H, d, J=5.9 Hz), 7.08 (1H, dd, J=8.8, 8.8 Hz), 7.56-7.65 (3H, m).

IR (KBr) cm⁻¹: 3401, 1658, 1648, 1618, 1602, 1501.

Mass m/z: 290 (M⁺).

7) Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1(9), 6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 91.4%).

Melting point: 114.6-117.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.29-2.40 (1H, m), 2.36 (3H, s), 3.17 (3H, s), 4.08 (2H, d, J=7.6 Hz), 5.27 (2H, d, J=1.5 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.56-7.69 (2H, m), 7.75 (1H, t, J=1.5 Hz).

IR (KBr) cm⁻¹: 1656, 1611, 1505, 1354, 1166.

Mass m/z: 368 (M⁺).

8) Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1(10), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a slightly yellow oil (yield: 79.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.27-2.40 (1H, m), 2.32 (3H, s), 2.36 (3H, d, J=2.0 Hz), 2.51 (4H, br), 2.62 (4H, br), 3.58 (2H, d, J=1.5 Hz), 4.07 (2H, d, J=7.3 Hz), 7.09 (1H, dd, J=8.8, 8.8 Hz), 7.58 (1H, ddd, J=2.0, 4.9, 8.8 Hz), 7.64 (1H, dd, J=2.0, 7.3 Hz), 7.73 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1652, 1609, 1503.

Mass m/z: 372 (M⁺).

Example 83 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless prisms (yield: 95.9%).

Melting point: 234.8-237.4° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.8 Hz), 2.19-2.30 (1H, m), 2.32 (3H, d, J=2.0 Hz), 2.81 (3H, s), 2.89-3.62 (10H, brm), 4.00(2H, d, J=7.3 Hz), 7.29(1H, dd, J=9.0, 9.0 Hz), 7.72-7.78 (1H, m), 7.83(1H, dd, J=2.4, 7.6 Hz), 8.31(1H, brs).

IR (KBr) cm⁻¹: 1660, 1609, 1504.

Example 84 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methylaminomethyl-2H-pyridazin-3-one

Following the procedure of Example 9(4), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow oil (yield: 96.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98(6H, d, J=6.8 Hz), 1.65 (1H, br), 2.29-2.42 (1H, m), 2.34 (3H, d, J=1.7 Hz), 2.51 (3H, s), 3.77 (2H, d, J=1.2 Hz), 4.07(2H, d, J=7.3 Hz), 7.07 (1H, dd, J=8.8, 8.8 Hz), 7.54-7.63 (2H, m), 7.64 (1H, t, J=1.2 Hz).

IR (Neat) cm⁻¹: 3306, 1653, 1605, 1507.

Mass m/z: 303 (M⁺).

Example 85 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methylaminomethyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methylaminomethyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless prisms (yield: 86.6%).

Melting point: 196.8-199.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.8 Hz), 2.19-2.31 (1H, m), 2.32 (3H, s), 2.65 (3H, s), 4.02 (2H, d, J=7.3 Hz), 4.12 (2H, s), 7.31 (1H, dd, J=8.5, 8.5 Hz), 7.72-7.78 (1H, m), 7.80-7.85 (1H, m), 8.32 (1H, s).

IR (KBr) cm⁻¹: 2722, 1652, 1615, 1505.

Example 86 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1(10), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and 1-benzylpiperazine were reacted to yield the title compound as a pale yellow oil (yield: 98.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.8 Hz), 2.29-2.39 (1H, m), 2.36 (3H, d, J=1.7 Hz), 2.55 (4H, br), 2.61 (4H, br), 3.55 (2H, s), 3.57 (2H, d, J=1.2 Hz), 4.06 (2H, d, J=7.6 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.23-7.34 (5H, m), 7.51 (1H, ddd, J=2.4, 4.8, 8.9 Hz), 7.63 (1H, dd, J=2.4, 7.2 Hz), 7.72 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1505.

Mass m/z: 448 (M⁺).

Example 87 Preparation of 4-(4-benzyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 4-(4-benzyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 95.3%).

Melting point: 259.1-263.1° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.17-2.29 (1H, m), 2.32 (3H, s), 2.55 (4H, br), 3.23-3.56 (8H, brm), 4.00 (2H, d, J=7.3 Hz), 4.11 (2H, brs), 4.38 (2H, brs), 7.29 (1H, dd, J=9.0, 9.0 Hz), 7.43-7.48 (3H, m), 7.59-7.65 (2H, m), 7.72-7.77 (1H, m), 7.79-7.84 (1H, m), 8.35 (1H, brs).

IR (KBr) cm⁻¹: 1660, 1618, 1612, 1453.

Example 88 Preparation of 4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow oil (yield: 96.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.28-2.39 (1H, m), 2.35 (3H, d, J=2.2 Hz), 2.56 (6H, s), 3.50 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 7.07 (1H, dd, J=8.9, 8.9 Hz), 7.59-7.67 (2H, m), 7.74 (1H, t, J=1.2 Hz).

IR (Neat) cm⁻¹: 1652, 1608, 1506.

Mass m/z: 317 (M⁺).

Example 89 Preparation of 4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 97.2%).

Melting point: 208.5-213.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.19-2.30 (1H, m), 2.32 (3H, s), 2.81 (6H, s), 4.03 (2H, d, J=7.0 Hz), 4.30 (2H, s), 7.30 (1H, dd, J=9.0, 9.0 Hz), 7.74-7.80 (1H, m), 7.85 (1H, m), 8.51 (1H, s).

IR (KBr) cm⁻¹: 1648, 1608, 1507.

Example 90 Preparation of 4-N,N′-bis(2-hydroxyethyl)aminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a slightly yellow oil (yield: 91.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.8 Hz), 2.27-2.40 (1H, m), 2.34 (3H, d, J=2.0 Hz), 2.70 (4H, t, J=5.0 Hz), 3.66 (4H, d, J=5.0 Hz), 3.69 (2H, s), 3.91 (2H, br), 4.07 (2H, d, J=7.6 Hz), 7.07 (1H, dd, J=8.9, 8.9 Hz), 7.60 (1H, ddd, J=2.2, 5.1, 8.9 Hz), 7.64 (1H, dd, J=2.2, 7.3 Hz), 7.71 (1H, s).

IR (Neat) cm⁻¹: 3391, 1654, 1371, 1505.

Mass m/z: 359 (M⁺−H₂O).

Example 91 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 92.4%).

Melting point: 155.1-157.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.20-2.31 (1H, m), 2.32 (3H, d, J=1.2 Hz), 3.35 (4H, br, overlapped with H2O), 3.82 (4H, br), 4.02 (2H, d, J=7.3 Hz), 4.50 (2H, s), 5.37 (2H, br), 7.30 (1H, dd, J=9.0, 9.0 Hz), 7.78 (1H, ddd, J=2.0, 4.9, 9.0 Hz), 7.85 (1H, dd, J=2.0, 7.3 Hz), 7.71 (1H, s).

IR (KBr) cm⁻¹: 3281, 1655, 1606.

Example 92 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(piperidino)methyl-2H-pyridazin-3-one

6-(4-Fluoro-3-methylphenyl)-2-isobutyl-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one (80 mg, 0.22 mmol) and piperidine (55 mg, 0.65 mmol) were dissolved in ethanol (0.5 mL), and the mixture was heated at 80° C. for 1 hour under stirring. The solvent was distilled off. The residue was purified by preparative thin-layer chromatography on silica gel [developing solvent: chloroform/methanol (10/1)] to yield the title compound as a slightly yellow oil (73 mg, 94.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.9 Hz), 1.45-1.53 (2H, m), 1.61-1.68 (4H, m), 2.28-2.41 (1H, m), 2.36 (3H, d, J=2.0 Hz), 2.47-2.53 (4H, m), 3.52 (2H, d, J=1.5 Hz), 4.07 (2H, d, J=7.3 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.59 (1H, ddd, J=1.7, 4.9, 8.9 Hz), 7.65 (1H, dd, J=1.7, 7.3 Hz), 7.76 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1652, 1616, 1506.

Mass m/z: 357 (M⁺).

Example 93 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(piperidino)methyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(piperidino)methyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow prisms (yield: 90.7%).

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 1.34-1.47 (1H, m), 1.64-1.73 (1H, m), 1.74-1.83 (4H, m), 2.20-2.30 (1H, m), 2.32 (3H, s), 2.95-3.02 (2H, m), 3.36-3.45 (1H, m), 4.02 (2H, d, J=7.3 Hz), 4.25 (2H, d, J=5.1 Hz), 7.30 (1H, dd, J=9.0, 9.0 Hz), 7.75-7.80 (1H, m), 7.83-7.87 (1H, m), 8.59 (1H, s).

IR (KBr) cm⁻¹: 2532, 1652, 1616, 1505, 1433.

Example 94 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(morpholino)methyl-2H-pyridazin-3-one

Following the procedure of Example 92, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and morpholine were reacted to yield the title compound as a slightly yellow oil (yield: 97.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.28-2.41 (1H, m), 2.36 (3H, d, J=2.0 Hz), 2.58 (4H, t, J=4.6 Hz), 3.57 (2H, d, J=1.2 Hz), 3.78 (4H, t, J=4.6 Hz), 4.07 (2H, d, J=7.3 Hz), 7.09 (1H, dd, J=8.8, 8.8 Hz), 7.58 (1H, ddd, J=2.0, 4.9, 8.8 Hz), 7.64 (1H, dd, J=2.0, 7.3 Hz), 7.75 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1659, 1606, 1503.

Mass m/z: 359 (M⁺).

Example 95 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(morpholino)methyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(morpholino)methyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless prisms (yield: 92.4%).

Melting point: 215.4-216.6° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.19-2.30 (1H, m), 2.32 (3H, s), 3.21 (2H, br), 3.79-3.98 (6H, m), 4.02 (2H, d, J=7.3 Hz), 4.33 (2H, brs), 7.30 (1H, dd, J=9.0, 9.0 Hz), 7.74-7.79 (1H, m), 7.81-7.86 (1H, m), 8.56 (1H, brs).

IR (KBr) cm⁻¹: 2392, 1647, 1607.

Example 96 Preparation of 4-aminomethyl-6-(4-fluoro-3-methyl-phenyl)-2-isobutyl-2H-pyridazin-3-one 1) Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-phthalimidomethyl-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 93.7%).

Melting point: 181.2-187.2° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 2.30 (3H, s), 4.07 (2H, d, J=7.3 Hz), 4.91 (2H, s), 7.01 (1H, dd, J=9.0, 9.0 Hz), 7.31 (1H, s), 7.41-7.46 (1H, m), 7.50-7.53 (1H, m), 7.76-7.81 (2H, m), 7.90-7.95 (2H, m).

IR (KBr) cm⁻¹: 1720, 1656, 1619, 1611.

Mass m/z: 419 (M⁺).

2) Preparation of 4-aminomethyl-6-(4-fluoro-3-methyl-phenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 24 (2), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-phthalimidomethyl-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow oil (yield: 99.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.64 (2H, br), 2.30-2.40 (1H, m), 2.35 (3H, d, J=2.0 Hz), 3.89 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 7.07 (1H, dd, J=8.8, 8.8 Hz), 7.60 (1H, ddd, J=2.1, 4.9, 8.8 Hz), 7.64 (1H, dd, J=2.1, 7.4 Hz), 7.67 (1H, t, J=1.2 Hz).

IR (Neat) cm⁻¹: 3372, 3301, 1655, 1605, 1504.

Mass m/z: 289 (M⁺).

Example 97 Preparation of 4-aminomethyl-6-(4-fluoro-3-methyl-phenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 79.8%).

Melting point: 217.5-220.5° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.20-2.30 (1H, m), 2.32 (3H, d, J=1.7 Hz), 4.01 (2H, d, J=2.2 Hz), 4.02 (2H, d, J=7.3 Hz), 7.31 (1H, dd, J=9.0, 9.0 Hz), 7.75 (1H, ddd, J=2.1, 4.9, 9.0 Hz), 7.83 (1H, dd, J=2.1, 7.4 Hz), 8.28 (1H, s).

IR (KBr) cm⁻¹: 2960, 2927, 2872, 1656, 1614, 1507.

Example 98 Preparation of 4-diethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethylamine were reacted to yield the title compound as a slightly yellow oil (yield: 94.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.07 (6H, t, J=7.1 Hz), 2.30-2.41 (1H, m), 2.35 (3H, d, J=1.5 Hz), 2.61 (4H, q, J=7.1 Hz), 3.60 (2H, d, J=1.7 Hz), 4.08 (2H, d, J=7.5 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.60 (1H, ddd, J=2.2, 4.9, 8.9 Hz), 7.65 (1H, dd, J=2.2, 7.3 Hz), 7.85 (1H, t, J=1.5 Hz).

IR (Neat) cm⁻¹: 1652, 1609, 1506.

Mass m/z: 345 (M⁺).

Example 99 Preparation of 4-diethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-diethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 70.1%).

Melting point: 154.3-157.3° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.92 (6H, d, J=6.8 Hz), 1.29 (6H, t, J=7.2 Hz), 2.20-2.30 (1H, m), 2.32 (3H, d, J=1.2 Hz), 3.09-3.25 (4H, m), 4.03 (2H, d, J=7.3 Hz), 4.28 (2H, d, J=5.6 Hz), 7.30 (1H, dd, J=9.0, 9.0 Hz), 7.80 (1H, ddd, J=2.0, 4.9, 9.0 Hz), 7.87 (1H, dd, J=2.0, 7.3 Hz), 7.85 (1H, t, J=1.5 Hz).

IR (KBr) cm⁻¹: 2559, 2491, 1652, 1613, 1507.

Example 100 Preparation of 4-(4-tert-butoxycarbonyl-1-pierazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-methanesulfonyloxy-methyl-2H-pyridazin-3-one and tert-butyl 1-piperazine-carboxylate were reacted to yield the title compound as a slightly yellow oil (yield: 97.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 1.46 (9H, s), 2.28-2.40 (1H, m), 2.36 (3H, d, J=1.7 Hz), 3.50 (4H, t, J=4.9 Hz), 3.58 (2H, d, J=1.0 Hz), 4.08 (2H, d, J=7.3 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.58 (1H, ddd, J=2.0, 4.9, 8.9 Hz), 7.63 (1H, dd, J=2.0, 7.3 Hz), 7.75 (1H, s).

IR (Neat) cm⁻¹: 1695, 1652, 1608, 1506.

Example 101 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-pierazinyl)methyl-6-(4-fluoro-3-methyl-phenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow oil (yield: quantitative).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.47 (1H, br), 2.28-2.40 (1H, m), 2.36 (3H, d, J=1.7 Hz), 2.56 (4H, t, J=4.9 Hz), 2.97 (4H, t, J=4.9 Hz), 3.56 (2H, d, J=1.4 Hz), 4.07 (2H, d, J=7.3 Hz), 7.09 (1H, dd, J=8.8, 8.8 Hz), 7.58 (1H, ddd, J=2.0, 4.9, 8.8 Hz), 7.64 (1H, dd, J=2.0, 7.3 Hz), 7.75 (1H, t, J=1.4 Hz).

Example 102 Preparation of 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(4-fluoro-3-methylphenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one was reacted toyield the title compound as pale yellow prisms (yield: 87.2%).

Melting point: 154.9-158.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.19-2.30 (1H, m), 2.32 (3H, d, J=1.7 Hz), 3.04 (4H, br), 3.71 (4H, br), 4.01 (2H, d, J=7.3 Hz), 7.28 (1H, dd, J=8.8, 8.8 Hz), 7.76 (1H, ddd, J=2.0, 4.9, 8.8 Hz), 7.83 (1H, dd, J=2.0, 7.3 Hz), 8.40 (1H, brs).

IR (KBr) cm⁻¹: 1659, 1610, 1504, 1422.

Example 103 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one 1) Preparation of ethyl 4-(3,4-difluorophenyl)-2-ethoxy-carbonyl-2-hydroxy-4-oxobutanoate

Following the procedure of Example 1 (3), 3′,4′-difluoroacetophenone was reacted to yield the title compound as a pale yellow oil (yield: 81.6%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30 (6H, t, J=7.1 Hz), 3.78 (2H, s), 4.22 (1H, s), 4.31 (4H, q, J=7.1 Hz), 7.24-7.30 (1H, m), 7.73-7.82 (2H, m).

IR (Neat) cm⁻¹: 3483, 1740, 1695, 1612.

Mass m/z: 312 (M⁺−H₂O).

2) Preparation of 4-carboxy-6-(3,4-difluorophenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (4), ethyl 4-(3,4-difluorophenyl)-2-ethoxycarbonyl-2-hydroxy-4-oxo-butanoate was reacted to yield the title compound as a pale yellow crystalline powder (yield: 88.9%).

3) Preparation of 4-methoxycarbonyl-6-(3,4-difluoromethyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (5), 4-carboxy-6-(3,4-difluorophenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 85.8%).

¹H NMR (400 MHz, CDCl₃) δ: 4.01 (3H, s), 7.25-7.32 (1H, m), 7.53-7.57 (1H, m), 7.67-7.73 (1H, m), 8.31 (1H, s), 11.70 (1H, br).

IR (KBr) cm⁻¹: 3223, 3159, 1722, 1676, 1659.

Mass m/z: 266 (M⁺).

4) Preparation of 6-(3,4-difluorophenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3,4-difluorophenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: quantitative).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H,d, J=6.8 Hz), 2.30-2.41 (1H, m), 3.98 (3H, s), 4.13 (2H, d, J=7.2 Hz), 7.23-7.30 (1H, m), 7.49-7.55 (1H, m), 7.68 (1H, ddd, J=2.2, 7.6, 11.1 Hz), 8.20 (1H, s).

5) Preparation of 4-carboxy-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 6-(3,4-difluorophenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine needles (yield: 91.4%).

Melting point: 163.4-163.7° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.02 (6H, d, J=6.6 Hz), 2.33-2.43 (1H, m),4.22 (2H, d, J=7.4 Hz), 7.27-7.35 (1H, m), 7.56-7.62 (1H, m), 7.74 (1H, ddd, J=2.4, 7.6, 11.2 Hz), 8.62 (1H, s), 14.05 (1H, s).

IR (KBr)^(cm) ⁻¹: 3436, 1737, 1635, 1522, 1434, 1276, 1102, 806.

Mass m/z: 308 (M⁺)

6) Preparation of 6-(3,4-difluorophenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 25.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.29-2.39 (1H, m), 2.96 (1H, t, J=5.9 Hz), 4.08 (2H,d, J=7.4 Hz), 4.72 (2H, dd, J=1.2, 5.8 Hz),7.22-7.28 (1H, m), 7.51-7.55 (1H, m), 7.64-7.71 (2H, m).

7) Preparation of 6-(3,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 6-(3,4-difluorophenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless fine-needles (yield: 81.4%).

Melting point: 113.3-113.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.27-2.40 (1H,m), 3.18 (3H, s), 4.08 (2H, d, J=7.4 Hz), 5.28 (2H, d, J=1.6 Hz), 7.23-7.30 (1H, m), 7.50-7.54. (1H, m), 7.68 (1H, ddd, J=2.2, 7.6, 11.1 Hz), 7.75 (1H, t, J=1.4 Hz).

IR (KBr) cm⁻¹: 3447, 1656, 1613, 1522, 1354, 1167, 1049, 877.

Mass m/z: 372 (M⁺)

8) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 85.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 1.47 (9H, s), 2.28-2.38 (1H, m), 2.52 (4H, t, J=4.7 Hz), 3.51 (4H, t, J=4.7 Hz), 3.58 (2H, s), 4.07 (2H, d, J=7.2 Hz), 7.21-7.29 (1H, m), 7.50-7-55 (1H, m), 7.64-7.71 (1H, m), 7.76 (1H, d, J=1.0 Hz).

Example 104 Preparation of 6-(3,4-difluorophenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 72.5%).

Melting point: 182.5-186.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.22-2.33 (1H, m), 3.11 (4H, br), 3.30 (4H, t, J=5.1 Hz), 3.90 (2H, s), 4.02 (2H, d, J=7.1 Hz), 7.52 (1H, ddd, J=8.6, 8.6, 10.5 Hz), 7.73-7.78 (1H, m), 7.90 (1H, ddd, J=2.2, 8.0, 11.7 Hz), 8.20 (1H, s).

IR (KBr) cm⁻¹: 1656, 1609, 1522, 1436, 1276, 1112.

Mass m/z: 362 (M⁺)

Example 105 Preparation of 6-(3,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 79.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.28-2.39 (1H, m), 2.34 (3H, s), 2.55 (4H, br), 2.63 (4H, br), 3.58 (2H, s), 4.07 (2H, d, J=7.2 Hz), 7.22-7.29 (1H, m), 7.50-7.57 (1H, m), 7.64-7.72 (1H, m), 7.74 (1H, s).

Example 106 Preparation of 6-(3,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(3,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 70.3%).

Melting point: 242.5-243.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.22-2.33 (1H, m), 2.77 (3H, s), 3.11 (4H, br), 3.34 (4H, br), 3.84 (2H, s), 4.02 (2H, d, J=7.1 Hz), 7.52 (1H, ddd, J=8.6, 8.6, 10.5 Hz), 7.72-7.77 (1H, m), 7.89 (1H, ddd, J=2.2, 7.9, 11.7 Hz), 8.12 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1522, 1435, 1278.

Mass m/z: 376 (M⁺)

Example 107 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 75.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.25-2.38 (1H, m), 2.70 (4H, br), 3.64-3.70 (6H, m), 4.06 (2H, d, J=7.4 Hz), 7.15-7.25 (1H, m), 7.54-7.58 (1H, m), 7.67-7.73 (1H, m), 7.88 (1H, s).

Example 108 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 70.3%).

Melting point: 127.5-128.3° C.

¹H NMR (400 MHz, DMSO₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.23-2.34 (1H, m), 3.35 (4H, t, J=5.1 Hz), 3.84 (4H, t, J=5.1 Hz), 4.05 (2H, d, J=7.1 Hz), 4.45 (2H, s), 7.54 (1H, ddd, J=8.6, 8.6, 10.5 Hz), 7.76-7.81 (1H, m), 7.93 (1H, m) 7.93(1H, ddd, J=2.2, 7.8, 12.0 Hz), 8.53 (1H, s).

IR (KBr) cm⁻¹: 1653, 1604, 1521, 1437, 1275.

Mass m/z: 363 (M⁺−H₂O)

Example 109 Preparation of 6-(3,4-difluorophenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(3,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 85.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.40 (1H, m), 2.35 (6H, s), 3.50 (2H, s), 4.07 (2H, d, J=7.4 Hz), 7.20-7.30 (1H, m), 7.53-7.60 (1H, m), 7.67-7.73 (1H, m), 7.74 (1H, s).

Example 110 Preparation of 6-(3,4-difluorophenyl)-4-dimethyl-aminomethyl-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(3,4-difluorophenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow flakes (yield: 85.9%).

Melting point: 226.5-227.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.8 Hz), 2.23-2.34 (1H, m), 2.81 (6H, s), 4.05 (2H, d, J=7.1 Hz), 4.28 (2H, s), 7.54 (ddd, J=8.7, 8.7, 10.5 Hz), 7.76-7.81 (1H, m), 7.93 (1H, ddd, J=2.2, 7.9, 12.0 Hz), 8.57 (1H, s)

IR (KBr) cm⁻¹: 1648, 1607, 1525, 1437, 1288, 1112.

Mass m/z: 321 (M⁺)

Example 111 Preparation of 4-aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one 1) Preparation of ethyl 4-(2,4-difluorophenyl)-2-ethoxy-carbonyl-2-hydroxy-4-oxobutanoate

Following the procedure of Example 1 (3), 2′,4′-difluoroacetophenone was reacted to yield the title compound as a pale yellow oil (yield: 76.8%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30 (6H, t, J=7.1 Hz), 3.81 (2H, d, J=3.4 Hz), 4.18 (1H, s), 4.30 (4H, q, J=7.1 Hz), 6.90 (1H, ddd, J=2.4, 8.5, 10.0 Hz), 6.94-7.00 (1H, m), 7.94 (1H, ddd, J=6.6, 8.5, 8.5 Hz).

IR (Neat) cm⁻¹: 3491, 1743, 1692, 1612.

Mass m/z: 312 (M⁺−H₂O)

2) Preparation of 4-carboxy-6-(2,4-difluorophenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (4), ethyl 4-(2,4-difluorophenyl)-2-ethoxycarbonyl-2-hydroxy-4-oxo-butanoate was reacted to yield the title compound as a pale yellow crystalline powder (yield: 95.2%).

3) Preparation of 6-(2,4-difluorophenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (5), 4-carboxy-6-(2,4-difluorophenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 81.2%).

¹H NMR (400 MHz, CDCl₃) δ: 3.99 (3H, s), 6.96 (1H, ddd, J=2.4, 8.8, 10.1 Hz), 6.99-7.04 (1H, m), 7.77 (1H, ddd, J=6.3, 8.8, 8.8 Hz), 8.30 (1H, d, J=2.0 Hz), 12.05 (1H, br).

IR (KBr) cm⁻¹: 3217, 3148, 1721, 1673, 1611.

Mass m/z: 266 (M⁺).

4) Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(2,4-difluorophenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow oil (yield: 84.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.29-2.42 (1H, m), 3.97 (3H, s), 4.12 (2H, d, J=7.3 Hz), 6.94 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.98-7.04 (1H, m), 7.73 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 8.18 (1H, d, J=2.0 Hz).

IR (Neat) cm⁻¹: 1755, 1748, 1668, 1620, 1506.

Mass m/z: 322 (M⁺).

5) Preparation of 4-carboxy-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 6-(2,4-difluorophenyl)-2-isobutyl-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 92.7%).

Melting point: 126.5-128.2° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.02 (6H, d, J=6.6 Hz), 2.31-2.43 (1H, m), 4.22 (2H, d, J=7.6 Hz), 6.96-7.07 (2H, m), 7.74 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 8.61 (1H, d, J=2.2 Hz), 14.02 (1H, s).

IR (KBr) cm⁻¹: 1739, 1636, 1618, 1573, 1465.

Mass m/z: 308 (M⁺).

6) Preparation of 6-(2,4-difluorophenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow oil (yield: 45.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.27-2.40 (1H, m), 3.15 (1H, t, J=6.1 Hz), 4.08 (2H, d, J=7.3 Hz), 4.69 (2H, dd, J=1.2, 6.1 Hz), 6.93 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.96-7.02 (1H, m), 7.61-7.63 (1H, m), 7.72 (1H, ddd, J=6.3, 6.3, 8.8 Hz).

IR (Neat) cm⁻¹: 3412, 1652, 1620, 1507.

Mass m/z: 294 (M⁺).

7) Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 6-(2,3-difluorophenyl)-4-hydroxymethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 96.3%).

Melting point: 86.7-88.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.26-2.39 (1H, m), 3.16 (3H, s), 4.08 (2H, d, J=7.3 Hz), 5.26 (2H, d, J=1.2 Hz), 6.94 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.97-7.03 (1H, m), 7.71 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 7.73-7.75 (1H, m).

IR (KBr) cm⁻¹: 1659, 1612, 1508, 1359, 1166.

Mass m/z: 372 (M⁺).

8) Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-phthalimidomethyl-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 91.1%).

Melting point: 152.3-155.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.28-2.39 (1H, m), 4.07 (2H, d, J=7.3 Hz), 4.89 (2H, d, J=1.0 Hz), 6.83 (1H, ddd, J=2.4, 8.8, 11.0 Hz), 6.91-6.97 (1H, m), 7.27-7.31 (1H, m), 7.66 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 7.74-7.80 (2H, m), 7.86-7.94 (2H, m).

IR (KBr) cm⁻¹: 1773, 1720, 1650, 1617, 1509, 1418, 1389.

Mass m/z: 423 (M⁺).

9) Preparation of 4-aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 24 (2), 2-isobutyl-6-(2,4-difluorophenyl)-4-phthalimidomethyl-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow oil (yield: 98.4%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.66 (2H, br), 2.24-2.41 (1H, m), 3.87 (2H, s), 4.08 (2H, d, J=7.3 Hz), 6.92 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.97-7.02 (1H, m), 7.63 (1H, t, J=1.1 Hz), 7.71 (1H, ddd, J=6.3, 6.3, 8.8 Hz).

IR (Neat) cm⁻¹: 3381, 3307, 1652, 1611, 1508.

Mass m/z: 293 (M⁺).

Example 112 Preparation of 4-aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 94.9%).

Melting point: 161.4-163.9° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.8 Hz), 2.18-2.34 (1H, m), 4.01 (2H, s), 4.02 (2H, d, J=7.3 Hz), 7.24-7.31 (1H, m), 7.46 (1H, ddd, J=2.4, 8.8, 11.5 Hz), 7.76 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 7.95 (1H, s)

IR (KBr) cm⁻¹: 1652, 1616, 1597, 1509.

Example 113 Preparation of 6-(2,4-difluorophenyl)-4-dimethyl-aminomethyl-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow oil (yield: 94.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 2.27-2.38 (1H, m), 2.34 (6H, s), 3.49 (2H, d, J=1.5 Hz), 4.07 (2H, d, J=7.6 Hz), 6.92 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.95-7.01 (1H, m), 7.70 (1H, t, J=1.5 Hz), 7.71 (1H, ddd, J=6.3, 6.3, 8.8 Hz).

IR (Neat) cm⁻¹: 1652, 1612, 1508.

Mass m/z: 321 (M⁺).

Example 114 Preparation of 6-(2,4-difluorophenyl)-4-dimethyl-aminomethyl-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 6-(2,4-difluorophenyl)-4-dimethylaminomethyl-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow prisms (yield: 89.8%).

Melting point: 170.1-173.5° C.

¹ H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 2.18-2.29 (1H, m), 2.80 (6H, s), 4.03 (2H, d, J=7.3 Hz), 4.30 (2H, s), 7.25-7.31 (1H, m), 7.45 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 7.81 (1H, ddd, J=6.3, 6.3, 8.8 Hz). 8.15 (1H, d, J=1.7 Hz),

IR (KBr) cm⁻¹: 1648, 1612, 1523, 1510.

Example 115 Preparation of 4-diethylaminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 9 (4), 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethylamine were reacted to yield the title compound as a pale yellow oil (yield: quantitative).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.06 (6H, t, J=7.1 Hz), 2.27-2.39 (1H, m), 2.59 (4H, q, J=7.1 Hz), 3.59 (2H, d, J=1.7 Hz), 4.07 (2H, d, J=7.3 Hz), 6.92 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.95-7.01 (1H, m), 7.72 (1H, ddd, J=6.3, 6.3, 8.8 Hz), 7.83 (1H, td, J=1.5, 2.9 Hz).

IR (Neat) cm⁻¹: 1656, 1613, 1508.

Mass m/z: 349 (M⁺).

Example 116 Preparation of 4-diethylaminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-diethylamino-methyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 80.9%).

Melting point: 128.9-131.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.8 Hz), 1.28 (6H, t, J=7.2 Hz), 2.18-2.29 (1H, m), 3.10-3.23 (4H, m), 4.03 (2H, d, J=7.3 Hz), 4.29 (2H, d, J=5.4 Hz), 7.28 (1H, ddd, J=2.2, 8.8, 8.8 Hz), 7.45 (1H, ddd, J=2.2, 8.8, 8.8 Hz), 7.81 (1H, ddd, J=6.3, 8.8, 8.8 Hz ), 8.24 (1H, d, J=1.5 Hz).

Example 117 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethy 1-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a slightly yellow oil (yield: 97.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.26-2.40 (1H, m), 2.70 (4H, t, J=5.0 Hz), 3.65 (4H, t, J=5.0 Hz), 3.70 (2H, s), 4.09 (2H, d, J=7.3 Hz), 6.92 (1H, ddd, J=2.7, 8.8, 11.2 Hz), 6.97-7.03 (1H, m), 7.63 (1H, d, J=2.4 Hz), 7.75 (1H, ddd, J=6.3, 6.3, 8.8 Hz).

IR (Neat) cm⁻¹: 3401, 1648, 1597, 1508.

Mass m/z: 363 (M⁺−H₂O).

Example 118 Preparation of 4-N,N-bis(2-hydroxy)aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxy)aminomethyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow prisms (yield: 89.0%).

Melting point: 161.8-163.9° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.18-2.29 (1H, m), 3.27-3.40 (4H, br, overlapped with H₂O), 3.76-3.84 (4H, m), 4.03 (2H, d, J=7.3 Hz), 4.51 (2H, brs), 5.34 (2H, br), 7.24-7.31 (1H, m), 7.41-7.48 (1H, m), 7.76-7.84 (1H, m), 8.15 (1H, m).

IR (KBr) cm⁻¹: 3233, 3172, 1645, 1613, 1593, 1421.

Example 119 Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a pale yellow oil (yield: 94.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.97 (6H, d, J=6.6 Hz), 2.28-2.38 (1H, m), 2.31 (3H, s), 2.50 (4H, br), 2.61 (4H, br), 3.57 (2H, d, J=1.5 Hz), 4.07 (2H, d, J=7.3 Hz), 6.93 (1H, ddd, J=2.4, 8.8, 11.2 Hz ), 6.96-7.02 (1H, m), 7.69-7.75 (2H, m).

IR (Neat) cm⁻¹: 1655, 1616, 1596, 1508.

Mass m/z: 376 (M⁺).

Example 120 Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(2,4-difluorophenyl)-2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 90.4%).

Melting point: 248.1-251.7° C. (dec.).

¹H NMR (400 MHz, DMSO-d₆, 100° C.) δ: 0.93 (6H, d, J=6.8 Hz), 2.20-2.29 (1H, m), 2.76 (3H, s), 3.09 (4H, br, overlapped with H₂O), 3.27 (4H, br), 3.74 (2H, s), 4.00 (2H, d, J=7.1 Hz), 7.14-7.29 (2H, m), 7.71-7.79 (2H, m).

IR (KBr) cm⁻¹: 1652, 1612, 1514.

Example 121 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(2,4-difluorophenyl)-2-isobutyl-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a slightly yellow oil (yield: 97.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.47 (9H, s), 2.28-2.39 (1H, m), 2.52 (4H, t, J=4.9 Hz), 3.49 (4H, t, J=4.9 Hz), 3.57 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 6.93 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.96-7.02 (1H, m), 7.69-7.75 (2H, m).

IR (Neat) cm⁻¹: 1695, 1655, 1613, 1508, 1425.

Mass m/z: 462 (M⁺).

Example 122 Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 20, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(2,4-difluorophenyl)-2-isobutyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: quantitative).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.8 Hz), 1.81 (1H, br), 2.27-2.39 (1H, m), 2.50-2.56 (4H, brm), 2.94 (4H, t, J=4.8 Hz ), 3.54 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.3 Hz), 6.93 (1H, ddd, J=2.4, 8.8, 11.2 Hz), 6.94-7.02 (1H, m), 7.69-7.76 (2H, m).

IR (Neat) cm⁻¹: 3314, 1655, 1613, 1508.

Mass m/z: 362 (M⁺).

Example 123 Preparation of 6-(2,4-difluorophenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 6-(2,4-difluorophenyl)-2-isobutyl-4-(1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow crystalline powder (yield: 90.8%).

Melting point: 136.3-140.9° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.93 (6H, d, J=6.6 Hz), 2.20-2.30 (1H, m), 2.95 (4H, t, J=5.0 Hz), 3.02 (4H, t, J=5.0 Hz), 3.76 (2H, s), 4.00 (2H, d, J=7.3 Hz), 7.14-7.20 (1H, m), 7.26 (1H, ddd, J=2.7, 8.8, 11.2 Hz), 7.86 (1H, ddd, J=6.6, 6.6, 8.8 Hz), 7.81 (1H, s).

IR (KBr) cm⁻¹: 1656, 1616, 1597, 1509, 1426.

Example 124 Preparation of 2-benzyl-4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one 1) Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and benzyl chloride were reacted to yield the title compound as yellow needles (yield: 71.0%).

Melting point: 109.0-110.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=1.7 Hz), 3.96 (3H, s), 5.44 (2H, s), 7.10 (1H, dd, J=8.8, 8.8 Hz), 7.28-7.37 (3H, m), 7.52 (2H, d, J=6.3 Hz), 7.57-7.64 (2H, m), 8.21 (1H, s).

IR (KBr) cm⁻¹: 1750, 1744, 1657, 1278, 1233, 1123.

Mass m/z: 352 (M⁺).

2) Preparation of 2-benzyl-4-carboxy-6-(4-fluoro-3-methyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 65.2%).

Melting point: 191.2-192.3° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.37 (3H, d, J=2.0 Hz), 5.52 (2H, s), 7.13 (1H, dd, J=8.8, 8.8 Hz), 7.33-7.41 (3H, m), 7.48-7.52 (2H, m), 7.64-7.70 (2H, m), 8.62 (1H, s), 14.01 (1H, br).

IR (KBr) cm⁻¹: 1739, 1633, 1569, 1457, 1423, 1240.

Mass m/z: 338 (M⁺).

3) Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 2-benzyl-4-carboxy-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 28.4%).

Melting point: 119.5-120.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.34 (3H, d, J=1.7 Hz), 3.01 (1H, t, J=5.9 Hz), 4.70 (2H, dd, J=1.2, 5.9 Hz), 5.41 (2H, s), 7.08 (1H, dd, J=8.8, 8.8 Hz), 7.27-7.37 (3H, m), 7.48 (1H, d, J=6.6 Hz), 7.57-7.65 (2H, m) 7.66 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3330, 1657, 1643, 1611, 1597, 1506, 1239.

Mass m/z: 324 (M⁺).

4) Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 98.9%).

Melting point: 147.6-148.3° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=2.0 Hz), 3.15 (3H, s), 5.26 (2H, d, J=1.2 Hz), 5.41 (2H, s), 7.09 (1H, dd, J=8.8, 8.8 Hz), 7.27-7.37 (3H, m), 7.47 (2H, d, J=6.6 Hz), 7.62 (1H, d, J=7.3 Hz), 7.57-7.60 (1H, m), 7.75 (1H, s).

IR (KBr) cm⁻¹: 1656, 1617, 1507, 1355, 1168, 1033, 879.

Mass m/z: 402 (M⁺).

5) Preparation of 2-benzyl-4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 91.8%).

¹H NMR (400 MHz, CDCl₃) δ: 1.46 (9H, s), 2.35 (3H, d, J=1.8 Hz), 2.50 (4H, t, J=4.9 Hz), 3.49 (4H, t, J=4.9 Hz), 3.56 (2H, d, J=1.4 Hz), 5.40 (2H, s), 7.26-7.36 (4H, m), 7.49 (2H, d, J=6.6 Hz), 7.55-7.60 (1H, m), 7.63 (1H, dd, J=1.8, 7.2 Hz), 7.74 (1H, s).

Example 125 Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 2-benzyl-4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 60.9%).

Melting point: 162.7-180.7° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=2.0 Hz), 3.09 (4H, br), 3.28 (4H, t, J=5.2 Hz), 3.89 (2H, s), 5.36 (2H, s), 7.21-7.40 (6H, m), 7.70-7.76 (1H, m), 7.79 (1H, dd, J=1.7, 7.3 Hz), 8.16 (1H, s).

IR (KBr) cm⁻¹: 1656, 1607, 1505, 1239, 1126, 700.

Mass m/z: 392 (M⁺)

Example 126 Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 81.3%).

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.36 (3H, d, J=1.8 Hz), 2.53 (4H, br), 2.61 (4H, br), 3.57 (2H, d, J=1.4 Hz), 5.40 (2H, s), 7.08 (1H, t, J=8.9 Hz), 7.26-7.36 (3H, m), 7.49 (2H, d, J=6.8 Hz), 7.56-7.60 (1H, m), 7.64 (1H, dd, J=1.8, 7.2 Hz), 7.73 (1H, s).

Example 127 Preparation of 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 78.6%).

Melting point: 240.0-242.5° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=1.7 Hz), 2.76. (3H, s), 3.10 (4H, br), 3.33 (4H, br), 3.84 (2H, s), 5.36 (2H, s), 7.21-7.39 (6H, m), 7.69-7.74 (1H, m), 7.78 (1H, dd, J=2.1, 7.8 Hz), 8.09 (1H, s)

IR (KBr) cm⁻¹: 1653, 1607, 1504, 1454, 1240, 1127.

Mass m/z: 406 (M⁺)

Example 128 Preparation of 2-benzyl-4-N,N-bis(2-hydroxyethyl)-aminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 87.6%).

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.69 (4H, t, J=4.9 Hz), 3.64 (4H, t, J=5.0 Hz), 3.68 (2H, s), 5.40 (2H, s), 7.06 (1H, t, J=8.9 Hz), 7.26-7.38 (3H, m), 7.45 (2H, d, J=7.0 Hz), 7.58-7.68 (2H, m), 7.75 (1H, s).

Example 129 Preparation of 2-benzyl-4-N,N-bis(2-hydroxyethyl)-aminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-benzyl-4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 75.9%).

Melting point: 161.7-163.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (2H, d, J=2.0 Hz), 3.34 (4H, t, J=5.2 Hz), 3.83 (4H, t, J=5.4 Hz), 4.47 (2H, s), 5.39 (2H, s), 7.23-7.40 (6H, m), 7.73-7.77 (1H, m), 7.82 (1H, dd, J=1.7, 7.3 Hz), 8.47 (1H, s).

IR (KBr) cm⁻¹: 1602, 1503, 1239, 1088.

Mass m/z: 393 (M⁺−H₂O)

Example 130 Preparation of 2-benzyl-4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-benzyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 92.7%).

¹H NMR (400 MHz, CDCl₃) δ: 2.34 (9H, s), 3.49 (2H, s), 5.40 (2H, s), 7.06 (1H, t, J=8.9 Hz), 7.25-7.35 (3H, m), 7.49 (2H, d, J=7.4 Hz), 7.58-7.67 (2H, m), 7.75 (1H, s).

Example 131 Preparation of 2-benzyl-4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-benzyl-4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as colorless flakes (yield: 72.6%).

Melting point: 225.3-226.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=2.0 Hz), 2.81 (6H, s), 4.28 (2H, s), 5.39 (2H, s), 7.21-7.41 (6H, m), 7.73-7.78 (1H, m), 7.83 (1H, dd, J=2.2, 7.6 Hz), 8.52 (1H, s).

IR (KBr) cm⁻¹: 1652, 1610, 1506, 1240, 1126, 702.

Mass m/z: 351 (M⁺)

Example 132 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one 1) Preparation of 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and cinnamyl bromide were reacted to yield the title compound as pale yellow needles (yield: 58.7%).

Melting point: 95.9-96.7° C.

¹ H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=1.7 Hz), 3.99 (3H, s), 5.04 (2H, dd, J=1.2, 6.8 Hz), 6.45 (1H, dt, J=15.9, 6.8 Hz), 6.75 (1H, d, J=15.9 Hz), 7.10 (1H, dd, J=8.9, 8.9 Hz), 7.20-7.33 (3H, m), 7.39 (2H, d, J=7.1 Hz), 7.58-7.66 (2H, m), 8.23 (1H, s).

IR (KBr) cm⁻¹: 1724, 1661, 1603, 1501, 1292, 1234, 1123.

Mass m/z: 378 (M⁺).

2) Preparation of 4-carboxy-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (yield: 85.1%).

Melting point: 142.8-143.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.36 (3H, d, J=2.0 Hz), 5.12 (2H, dd, J=1.2, 6.8 Hz), 6.42 (1H, dt, J=15.9, 6.8 Hz), 6.80 (1H, d, J=15.9 Hz), 7.13 (1H, dd, J=8.8, 8.8 Hz), 7.22-7.36 (3H, m), 7.40-7.43 (2H, m), 7.65-.7.72 (2H, m), 8.64 (1H, s), 14.04 (1H, br).

IR (KBr) cm⁻¹: 3438, 3061, 2688, 1747, 1637, 1567, 1463, 1244.

Mass m/z: 364 (M⁺).

3) Preparation of 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 20.1%).

Melting point: 139.9-140.9° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.34 (3H, d, J=1.5 Hz), 3.00 (1H, br), 4.73 (2H, s), 5.01 (2H, d, J=6.6 Hz), 6.44 (1H, dt, J=15.9, 6.6 Hz), 6.72 (2H, d, J=15.9 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.24 (1H, t, J=7.3 Hz), 7.30 (2H, dd, J=7.3, 7.3 Hz), 7.39 (2H, d, J=7.3 Hz), 7.58-7.62 (1H, m), 7.64 (1H, d, J=7.3 Hz), 7.67 (1H, s).

IR (KBr) cm⁻¹: 3393, 1655, 1648, 1602, 1505, 1451, 1238, 1077.

Mass m/z: 350 (M⁺).

4) Preparation of 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 91.9%).

Melting point: 78.4-80.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=2.0 Hz), 3.17 (3H, s), 5.10 (2H, dd, J=1.2, 6.8 Hz), 5.28 (2H, d, J=1.2 Hz), 6.42 (1H, dt, J=15.9, 6.8 Hz), 6.73 (1H, d, J=15.9 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.21-7.33 (3H, m), 7.40 (2H, d, J=8.8 Hz), 7.57-7.62 (1H, m), 7.64 (1H, d, J=8.8 Hz), 7.77 (1H, t, J=1.3 Hz).

IR (KBr) cm⁻¹: 1663, 1612, 1508, 1355, 1241, 1167, 988, 958, 873.

Mass m/z: 428 (M⁺).

5) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 86.7%).

¹H NMR (400 MHz, CDCl₃) δ: 1.47 (9H, s), 2.35 (3H, d, J=1.6 Hz), 2.52 (4H, t, J=5.0 Hz), 3.51 (4H, t, J=4.9 Hz), 3.59 (2H, d, J=1.4 Hz), 5.00 (2H, dd, J=1.0, 6.6 Hz), 6.45 (1H, dt, J=15.8, 6.6 Hz), 6.72 (1H, d, J=15.8 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.22 (1H, t, J=7.2 Hz), 7.29 (2H, dd, J=7.0, 7.0 Hz), 7.38 (2H, d, J=7.7 Hz), 7.56-7.61 (1H, m), 7.65 (1H, dd, J=1.8, 7.2 Hz), 7.77 (1H, s).

Example 133 Preparation of 2-cinnamyl-6-(4-fluoro-3-methyl-phenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 96.0%).

Melting point: 171.1-187.1° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=2.0 Hz), 3.21 (4H, t, J=4.9 Hz), 3.34 (4H, t, J=5.1 Hz), 3.99 (2H, s), 4.95 (2H, dd, J=1.3, 6.4 Hz), 6.45 (1H, dt, J=16.1, 6.3 Hz), 6.68 (1H, d, J=16.1 Hz), 7.20-7.26 (2H, m), 7.29-7.34 (2H, m), 7.41-7.45 (2H, m), 7.73-7.79 (1H, m), 7.83 (1H, dd, J=1.7, 7.3 Hz), 8.26 (1H, s).

IR (KBr) cm⁻¹: 1656, 1605, 1505, 1239, 962.

Mass m/z: 418 (M⁺)

Example 134 Preparation of 2-cinnamyl-6-(4-fluoro-3-methyl-phenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 80.1%).

¹H NMR (400 MHz, CDCl₃) δ: 2.32 (3H, s), 2.35 (3H, d, J=1.8 Hz), 2.51 (4H, br), 2.62 (4H, br), 3.59 (2H, d, J=1.4 Hz), 4.99 (2H, dd, J=1.1, 6.6 Hz), 6.45 (1H, dt, J=15.8, 6.0 Hz), 6.72 (1H, d, J=15.8 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.22 (1H, tt, J=1.6, 7.2 Hz), 7.29 (2H, dd, J=7.2, 7.2 Hz), 7.39 (2H, dd, J=1.4, 7.2 Hz), 7.56-7.61 (1H, m), 7.65 (1H, dd, J=1.8, 7.2 Hz), 7.75 (1H, t, J=1.4 Hz).

Example 135 Preparation of 2-cinnamyl-6-(4-fluoro-3-methyl-phenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 66.3%).

Melting point: 236.1-237.1° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, d, J=2.2 Hz), 2.76 (3H, s), 3.08 (4H, br), 3.32 (4H, br), 3.83 (2H, s), 4.94 (2H, dd, J=1.2, 6.4 Hz), 6.45 (1H, dt, J=16.1, 6.3 Hz), 6.67 (1H, d, J=15.8 Hz), 7.19-7.26 (2H, m), 7.29-7.34 (2H, m), 7.41-7.44 (2H, m), 7.71-7.76 (1H, m), 7.81 (1H, dd, J=2.2, 7.6 Hz), 8.07 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1505, 1239, 1129.

Mass m/z: 432 (M⁺)

Example 136 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 83.7%).

¹H NMR (400 MHz, CDCl₃) δ: 2.32 (3H, s), 2.69 (4H, t, J=4.9 Hz), 3.65 (4H, d, J=4.9 Hz), 3.69 (2H, s), 4.98 (2H, d, J=6.6 Hz), 6.41 (1H, dt, J=15.8, 6.5 Hz), 6.68 (1H, d, J=15.8 Hz), 7.05 (1H, dd, J=8.9, 8.9 Hz), 7.21 (1H, t, J=7.2 Hz), 7.28 (2H, dd, J=7.2, 7.2 Hz), 7.37 (2H, d, J=7.6 Hz), 7.58-7.63 (1H, m), 7.66 (1H, dd, J=1.8, 7.2 Hz), 7.81 (1H, s)

Example 137 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cinnamyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cinnamyl-6-(4-fluoro -3-methyl-phenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 63.2%).

Melting point: 112.5-113.2° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, d, J=1.9 Hz), 3.35 (4H, t, J=5.1 Hz), 3.84 (4H, t, J=5.1 Hz), 4.46 (2H, s), 4.98 (2H, dd, J=1.5, 6.1 Hz), 6.45 (1H, dt, J=15.8, 6.1 Hz), 6.69 (1H, d, J=16.0 Hz), 7.21-7.27 (2H, m), 7.29-7.34 (2H, m), 7.41-7.44 (2H, m), 7.757.80 (1H, m), 7.85 (1H, dd, J=2.0, 7.3 Hz), 8.47 (1H, s).

IR (KBr) cm⁻¹: 1652, 1604, 1505, 1241, 971.

Mass m/z: 419 (M⁺−H₂O)

Example 138 Preparation of 2-cinnamyl-4-dimethylaminomethyl-6-(4-fluoro-3-methyl phenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-cinnamyl-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 90.9%).

¹H NMR (400 MHz, CDCl₃) δ: 2.34 (3H, d, J=2.0 Hz), 2.36 (6H, s), 3.51 (2H, d, J=1.4 Hz), 5.00 (2H, dd, J=1.3, 6.8 Hz), 6.46 (1H, dt, J=15.8, 6.6 Hz), 6.72 (1H, d, J=15.8 Hz), 7.07 (1H, dd, J=8.9, 8.9 Hz), 7.22 (1H, tt, J=1.4, 7.2 Hz), 7.29 (2H, dd, J=7.2, 7.2 Hz), 7.39 (2H, dd, J=1.6, 7.0 Hz), 7.60-7.65 (1H, m), 7.67 (1H, dd, J=2.2, 7.2 Hz), 7.76 (1H, s).

Example 139 Preparation of 2-cinnamyl-4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cinnamyl-4-dimethylaminomethyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 81.1%).

Melting point: 183.6-184.5° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, d, J=2.0 Hz), 2.83 (6H, s), 4.29 (2H, s), 4.98 (2H, dd, J=1.3, 6.4 Hz), 6.46 (1H, dt, J=16.1, 6.3 Hz), 6.69 (1H, d, J=16.1 Hz), 7.22-7.27 (2H, m), 7.297.35 (2H, m), 7.41-7.44 (2H, m), 7.76-7.81 (1H, m), 7.86 (1H, dd, J=2.2, 7.3 Hz), 8.50 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1505, 1240, 965.

Mass m/z: 377 (M⁺)

Example 140 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one 1) Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and 4-chlorocinnamyl chloride were reacted to yield the title compound as yellow needles (yield: 71.7%).

Melting point: 137.8-138.8° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=1.7 Hz), 3.99 (3H, s), 5.03 (2H, d, J=6.6 Hz), 6.43 (1H, dt, J=15.6, 6.6 Hz), 6.70 (1H, d, J=15.6 Hz), 7.10 (1H, d, J=8.8 Hz), 7.27 (2H, d, J=8.8 Hz), 7.31 (2H, d, J=8.8 Hz), 7.58-7.63 (1H, m), 7.64 (1H, dd, J=2.1, 7.0 Hz), 8.24 (1H, s).

IR (KBr) cm⁻¹: 1724, 1709, 1667, 1506, 1291, 1236, 1126, 831.

Mass m/z: 412 (M⁺), 414 (M⁺).

2) Preparation of 4-carboxy-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-(4-chloro-cinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow crystalline powder (yield: 86.2%).

Melting point: 186.0-186.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.36 (3H, d, J=2.0 Hz), 5.11 (2H, dd, J=1.2, 6.8 Hz), 6.39 (1H, dt, J=15.9, 6.8 Hz), 6.75 (1H, d, J=15.6 Hz), 7.13 (1H, dd, J=8.8, 8.8 Hz), 7.29 (2H, d, J=8.5 Hz), 7.33 (2H, d, J=8.5 Hz), 7.65-7.71 (2H, m), 8.64 (1H, s), 13.98 (1H, br).

IR (KBr) cm⁻¹: 3471, 1738, 1631, 1566, 1490, 1467, 1403, 1242, 812, 802.

Mass m/z: 398 (M⁺), 400 (M⁺).

3) Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly yellow needles (yield: 17.2%).

Melting point: 131.8-133.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.34 (3H, d, J=2.0 Hz), 4.73 (2H, d, J=1.2 Hz), 4.99 (2H, dd, J=1.0, 6.6 Hz), 6.40 (1H, dt, J=15.9, 6.6 Hz), 6.75 (1H, d, J=15.9 Hz), 7.08 (1H, dd, J=8.9, 8.9 Hz), 7.26 (2H, d, J=8.8 Hz), 7.31 (2H, d, J=8.8. Hz), 7.57-7.62 (1H, m), 7.64 (1H, dd, J=2.2, 7.3 Hz), 7.69 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3359, 1653, 1598, 1506, 1492, 1240, 1091, 1076.

Mass m/z: 384 (M⁺), 386 (M⁺).

4) Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-hydroxy-methyl-2H-pyridazin-3-one was reacted to yield the title compound as colorless needles (yield: 94.9%).

Melting point: 117.8-119.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (3H, d, J=2.0 Hz), 3.17 (3H, s), 4.99 (2H, dd, J=1.2, 6.6 Hz), 5.28 (2H, d, J=1.2 Hz), 6.38 (1H, dt, J=15.9, 6.6 Hz), 6.75 (1H, d, J=15.9 Hz), 7.10 (1H, dd, J=8.8, 8.8 Hz), 7.27 (2H, d, J=8.5 Hz), 7.32 (2H, d, J=8.5. Hz), 7.57-7.65 (2H, m), 7.78 (1H, t, J=1.3 Hz).

IR (KBr) cm⁻¹: 1663, 1619, 1506, 1492, 1346, 1240, 1172, 960, 830.

Mass m/z: 462 (M⁺), 464 (M⁺).

5) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methyl-phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 87.9%).

¹H NMR (400 MHz, CDCl₃) δ: 1.47 (9H, s), 2.35 (3H, d, J=1.6 Hz), 2.52 (4H, t, J=4.9 Hz), 3.50 (4H, t, J=5.0 Hz), 3.59 (2H, d, J=1.2 Hz), 4.99 (2H, dd, J=1.0, 6.6 Hz), 6.42 (1H, dt, J=15.8, 6.6 Hz), 6.67 (1H, d, J=16.0 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.25 (2H, d, J=8.8 Hz), 7.31 (2H, d, J=8.6 Hz), 7.55-7.61 (1H, m), 7.64 (1H, dd, J=2.0, 7.2 Hz), 7.77 (1H, s).

Example 141 Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale brown crystalline powder (yield: 84.7%).

Melting point: 186.7-197.0° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=2.0 Hz), 3.15 (4H, br), 3.31 (4H, t, J=5.2 Hz), 3.94 (2H, s), 4.95 (2H, dd, J=1.3, 6.3 Hz), 6.47 (1H, dt, J=15.9, 6.1 Hz), 6.66 (1H, d, J=15.9 Hz), 7.22 (1H, dd, J=9.0, 9.0 Hz), 7.34 (2H, d, J=8.6 Hz), 7.45 (2H, d, J=8.6 Hz), 7.73-7.78 (1H, m), 7.82 (1H, dd, J=1.9, 7.6 Hz), 8.21 (1H, s).

IR (KBr) cm⁻¹: 1656, 1606, 1240, 1090, 964.

Mass m/z: 452 (M⁺), 454 (M⁺).

Example 142 Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methane-sulfonyloxymethyl-2 2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 71.8%).

¹H NMR (400 MHz, CDCl₃) δ: 2.32 (3H, s), 2.35 (3H, s), 2.51 (4H, br), 2.62 (4H, br), 3.59 (2H, s), 4.99 (2H, d, J=6.6 Hz), 6.42 (1H, dt, J=15. 8, 6.4 Hz), 6.66 (1H, d, J=15.9 Hz), 7.09 (1H, dd, J=8.9, 8.9 Hz), 7.24 (2H, d, J=8.6 Hz), 7.30 (2H, d, J=8.6 Hz), 7.56-7.62 (1H, m), 7.65 (1H, dd, J=1.8, 7.2 Hz), 7.76 (1H, s).

Example 143 Preparation of 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-(4-chloro-cinnamyl)-6-(4-fluoro-3-methylphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 80.4%).

Melting point: 229.7-243.3° (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 2.31 (3H, d, J=1.8 Hz), 2.76 (3H, s), 3.09 (4H, br), 3.33 (4H, br), 3.83 (2H, s), 4.94 (2H, dd, J=1.2, 6.0 Hz), 6.42 (1H, dt, J=16.0, 6.2 Hz), 6.65 (1H, d, J=16.0 Hz), 7.22 (1H, dd, J=9.1, 9.1 Hz), 7.34 (2H, d, J=8.6 Hz), 7.45 (2H, d, J=8.6 Hz), 7.71-7.76 (1H, m), 7.80 (1H, dd, J=2.2, 7.0 Hz), 8.08 (1H, s).

IR (KBr) cm⁻¹: 1652, 1608, 1492, 1239, 1130.

Mass m/z: 466 (M⁺), 468 (M⁺).

Example 144 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 76.6%).

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.70 (4H, t, J=4.5 Hz), 3.66 (4H, t, J=4.9 Hz), 3.70 (2H, s), 4.98 (2H, d, J=6.6 Hz), 6.36 (1H, dt, J=15.8, 6.5 Hz), 6.63 (1H, d, J=15.8 Hz), 7.06 (1H, dd, J=8.6, 8.6 Hz), 7.24 (2H, d, J=8.6 Hz), 7.30 (2H, d, J=8.2 Hz), 7.58-7.63 (1H, m), 7.65 (1H, dd, J=1.8, 7.2 Hz), 7.78 (1H, s).

Example 145 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-(4-chlorocinnamyl)-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 76.1%).

Melting point: 151.9-153.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, d, J=1.7 Hz), 3.35 (4H, t, J=5.1 Hz), 3.83 (4H, t, J=5.4 Hz), 4.46 (2H, s), 4.97 (2H, dd, J=1.2, 6.1 Hz), 6.48 (1H, dt, J=15.9, 6.2 Hz), 6.67 (1H, d, J=15.9 Hz), 7.24 (1H, dd, J=9.1, 9.1 Hz), 7.35 (2H, d, J=8.8 Hz), 7.45 (2H, d, J=8.6 Hz), 7.75-7.80 (1H, m), 7.85 (1H, dd, J=1.7, 7.9 Hz), 8.48 (1H, s).

IR (KBr) cm⁻¹: 1652, 1604, 1492, 1240, 1090, 968.

Mass m/z: 440 (M⁺), 442 (M⁺).

Example 146 Preparation of 2-(4-chlorocinnamyl)-4-dimethylamino-methyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-(4-chloro-cinnamyl)-6-(4-fluoro-3-methylphenyl)-4-methane-sulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 84.6%).

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, d, J=1.6 Hz), 2.36 (6H, s), 3.52 (2H, d, J=1.2 Hz), 4.99 (2H, dd, J=1.0, 6.6 Hz), 6.43 (1H, dt, J=15.8, 6.6 Hz), 6.66 (1H, d, J=15.8 Hz), 7.07 (1H, dd, J=8.9, 8.9 Hz), 7.24 (2H, d, J=8.6 Hz), 7.30 (2H, d, J=8.6 Hz), 7.60-7.68 (2H, m), 7.77 (1H, s).

Example 147 Preparation of 2-(4-chlorocinnamyl)-4-dimethylamino-methyl-6-(4-fluoro-3-methylphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-(4-chloro-cinnamyl)-4-dimethylaminomethyl-6-(4-fluoro-3-methyl-phenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 34.4%).

Melting point: 201.3-201.9° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.32 (3H, d, J=1.7 Hz), 2.83 (6H, s), 4.28 (2H, s), 4.98 (2H, dd, J=1.3, 6.1 Hz), 6.48 (1H, dt, J=16.1, 6.1 Hz), 6.67 (1H, d, J=16.1 Hz), 7.24 (1H, dd, J=9.3, 9.3 Hz), 7.35 (2H, d, J=8.6 Hz), 7.45 (2H, d, J=8.6 Hz), 7.75-7.80 (1H, m), 7.85 (1H, dd, J=2.3, 7.6 Hz), 8.47 (1H, s).

IR (KBr) cm⁻¹: 1652, 1608, 1491, 1239, 968.

Mass m/z: 411 (M⁺), 413 (M⁺).

Example 148 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylthio) phenyl]-2H-pyridazin-3-one 1) Preparation of 4-carboxy-2-cyclopropylmethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-cyclopropylmethyl-4-methoxycarbonyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow crystalline powder (yield: 98.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.50-0.66 (4H, m), 1.40-1.53 (1H, m), 2.54 (3H, s), 4.24 (2H, d, J=7.4 Hz), 7.34 (2H, d, J=8.6 Hz), 7.78 (2H, d, J=8.6 Hz), 8.66 (1H, s), 14.22 (1H, s).

IR (KBr) cm⁻¹: 3430, 1752, 1631, 1472, 1452, 1403, 1093, 825.

Mass m/z: 316 (M⁺)

2) Preparation of 2-cyclopropylmethyl-4-hydroxymethyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-cyclopropylmethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 22.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.60 (4H, m), 1.37-1.46 (1H, m), 2.53 (3H, s), 3.09 (1H, t, J=6.1 Hz), 4.11 (2H, d, J=7.2 Hz), 4.72 (2H, d, J=6.0 Hz), 7.32 (2H, d, J=8.6 Hz), 7.67 (1H, s), 7.74 (2H, d, J=8.6 Hz).

IR (KBr) cm⁻¹: 3393, 1657, 1602, 1514, 1095, 822.

Mass m/z: 302 (M⁺). 3) Preparation of 2-cyclopropylmethyl-4-methanesulfonyloxy-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-cyclopropylmethyl-4-hydroxymethyl-6-[4-(methylthio)phenyl ]-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow fine-needles (yield: 78.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-1.61 (4H, m), 1.37-1.47 (1H, m), 2.53 (3H, s), 3.17 (3H, s), 4.11 (2H, d, J=7.2 Hz), 5.28 (2H, s), 7.33 (2H, d, J=8.4 Hz), 7.74 (2H, d, J=8.4 Hz), 7.79 (1H, s).

IR (KBr) cm⁻¹: 3446, 1652, 1607, 1359, 1178, 1024, 829.

Mass m/z: 380 (M⁺).

4) Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one and 1-methyl-piperazine were reacted to yield the title compound as a yellow oil (yield: 85.7 %)

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.58 (4H, m), 1.36-1.48 (1H, m), 2.33 (3H, s), 2.53 (3H, s), 2.47-2.66 (8H, m), 3.59 (2H, s), 4.10 (2H, d, J=7.3 Hz), 7.33 (2H, d, J=8.3 Hz), 7.75 (2H, d, J=8.3 Hz), 7.78 (1H, s).

Example 149 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[[4-(methylthio)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 69.1%).

Melting point: 234.6-239.2° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.40-0.45 (2H, m), 0.50-0.56 (2H, m), 1.30-1.40 (1H, m), 2.53 (3H, s), 2.77 (3H, s), 2.97 (4H, br), 3.28 (4H, br), 3.72 (2H, s), 4.05 (2H, d, J=7.1 Hz), 7.39 (2H, d, J=8.6 Hz), 7.82 (2H, d, J=8.3 Hz), 7.96 (1H, s).

IR (KBr) cm⁻¹: 3438, 1651, 1606, 1402, 1095.

Mass m/z: 384 (M⁺).

Example 150 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-4-methanesulfonyloxymethyl-6-[4-(methyl thio)phenyl)-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 78.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.59 (4H, m), 1.36-1.45 (1H, m), 2.53 (3H, s), 2.73 (4H, br), 3.67 (4H, t, J=4.9 Hz), 3.73 (2H, s), 4.13 (2H, d, J=7.3 Hz), 7.32 (2H, d, J=8.3 Hz), 7.70 (1H, s), 7.74 (2H, d, J=8.3 Hz).

Example 151 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopropylmethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a slightly yellow solid (yield: 75.1%).

Melting point: 169.2-171.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.42-0.46 (2H, m), 0.52-0.57 (2H, m), 1.30-1.40 (1H, m), 2.53 (3H, s), 3.31 (4H, br), 3.81 (4H, t, J=5.3 Hz), 4.42 (2H, s), 7.41 (2H, d, J=8.8 Hz), 7.85 (2H, d, J=9.0 Hz), 8.37 (1H, s).

IR (KBr) cm⁻¹: 3242, 1652, 1604, 1420, 1094, 1059, 823.

Mass m/z: 358 (M⁺−CH₂OH).

Example 152 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 7, 2-cyclopropyl-methyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 98.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.58 (4H, m), 1.36-1.48 (1H, m), 2.35 (6H, s), 3.51 (2H, s), 4.51 (2H, d, J=7.3 Hz), 7.31 (2H, d, J=8.3 Hz), 7.77 (2H, d, J=7.8 Hz), 7.78 (1H, s).

Example 153 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-dimethylaminomethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 75.5%). Melting point: 230.2-232.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.42 -0.46 (2H, m), 0.52-0.58 (2H, m), 1.31-1.40 (1H, m), 2.53 (3H, s), 2.82 (6H, s), 4.09 (2H, d, J=7.1 Hz), 4.25 (2H, s), 7.41 (2H, d, J=8.6 Hz), 7.84 (2H, d, J=8.5 Hz), 8.34 (1H, s).

IR (KBr) cm⁻¹: 3435, 1646, 1604, 1402, 1093, 829.

Mass m/z: 329 (M⁺).

Example 154 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-[4-(methylthio)-phenyl)-2H-pyridazin-3-one 1) Preparation of 4-carboxy-2-isobutyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one

To a solution of 4-methoxycarbonyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one (8.00 g, 29.0 mmol) in N,N-dimethylformamide (80 mL) were added potassium carbonate (8.02 g, 58.0 mmol) and isobutyl bromide (4.76 g, 34.8 mmol), and the mixture was stirred at 80° C. for 2 hours. The temperature of the reaction mixture was allowed to drop back to room temperature, and a saturated aqueous solution of sodium hydrogencarbonate was added. The mixture was then extracted with ethyl acetate. The extract was washed with brine, and dried over anhydrous sodium sulfate. The solvent was distilled off. Following the procedure of Example 1 (7), the residue was reacted to yield the title compound as a yellow solid [yield: 65.1% (2 steps)].

¹H NMR (400 MHz, CDCl₃) δ: 1.01 (6H, d, J=6.6 Hz), 2.33-2.46 (1H, m), 2.54 (3H, s), 4.21 (2H, d, J=7.4 Hz), 7.34 (2H, d, J=8.4 Hz), 7.80 (2H, d, J=8.4 Hz), 8.68 (1H, s), 12.72 (1H, s).

Mass m/z: 318 (M⁺).

2) Preparation of 4-hydroxymethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-isobutyl-6-[4-(methylthio)phenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 35.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.27-2.39 (1H, m), 2.53 (3H, s), 4.08 (2H, d, J=7.4 Hz), 4.71 (2H, d, J=5.9 Hz), 7.26 (2H, d, J=8.4 Hz), 7.66 (1H, s), 7.73 (2H, d, J=8.6 Hz).

3) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 4-hydroxymethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 73.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.28-2.40 (1H, m), 2.53 (3H, s), 3.17 (3H, s), 4.08 (2H, d, J=7.4 Hz), 5.27 (2H, d, J=1.2 Hz), 7.32 (2H, d, J=8.4 Hz), 7.73 (2H, d, J=8.4 Hz), 7.75 (1H, d, J=1.4 Hz).

Mass m/z: 382 (M⁺).

4) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-2-isobutyl-6-[4-(methylthio)phenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-6-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 88.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 1.47 (9H, s), 2.28-2.40 (1H, m), 2.50-2.55 (4H, m), 2.53 (3H, s), 3.50 (4H, t, J=4.8 Hz), 3.58 (2H, s), 4.07 (2H, d, J=7.4 Hz), 7.32 (2H, d, J.=8.4 Hz), 7.73 (2H, d, J=8.6 Hz), 7.78 (1H, s).

Example 155 Preparation of 2-isobutyl-6-[4-(methylthio)phenyl]-4-(1-piperazinyl) methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow crystalline powder (yield: 70.5%).

Melting point: 248.5-253.7° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.6 Hz), 2.21-2.33 (1H, m), 2.52 (3H, s), 3.10 (4H, t, J=4.8 Hz), 3.30 (4H, t, J=5.2 Hz), 3.90 (2H, s), 4.01 (2H, d, J=7.3 Hz), 7.39 (2H, d, J=8.3 Hz), 7.83 (2H, d, J=8.3 Hz), 8.15 (1H, s).

IR (KBr) cm⁻¹: 2961, 2442, 1640, 1596, 1511, 1433, 1406, 1089, 912.

Mass m/z: 372 (M⁺).

Example 156 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 68.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.39 (1H, m), 2.32 (3H, s), 2.51 (4H, br), 2.53 (3H, s), 2.62 (4H, br), 3.58 (2H, d, J=1.4 Hz), 4.07 (2H, d, J=7.4 Hz), 7.33 (2H, d, J=8.6 Hz), 7.74 (2H, d, J=6.8 Hz), 7.76 (1H, s).

Example 157 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 86.4%).

Melting point: 242.6-243.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.21-2.33 (1H, m), 2.52 (3H, s), 2.76 (3H, s), 3.09 (4H, br), 3.33 (4H, br), 3.83 (2H, s), 4.01 (2H, d, J=7.1 Hz), 7.39 (2H, d, J=8.6 Hz), 7.82 (2H, d, J=8.5 Hz), 8.07 (1H, s).

IR (KBr) cm⁻¹: 3432, 2957, 2437, 1652, 1607, 1090, 953.

Mass m/z: 386 (M⁺).

Example 158 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 71.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.96 (6H, d, J=6.6 Hz), 2.27-2.39 (1H, m), 2.51 (3H, s), 2.71 (4H, t, J=5.1 Hz), 3.66 (4H, t, J=5.1 Hz), 3.70 (2H, s), 4.08 (2H, d, J=7.2 Hz), 7.30 (2H, d, J=8.6 Hz), 7.71-7.76 (3H, m).

Example 159 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one oxalate

To a solution of 4-N,N-bis (2-hydroxyethyl) amino-methyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one (69.7 mg, 0.18 mmol) in methanol (1 mL) was added at room temperature oxalic acid dihydrate (22.4 mg, 0.18 mmol). The solvent was distilled off. The residue was recrystallized from chloroform-diethyl ether to obtain the title compound as a white solid (59.5 mg, 69.4%).

Melting point: 116.4-118.1° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.94 (6H, d, J=6.6 Hz), 2.20-2.33 (1H, m), 2.52 (3H, s), 2.91 (4H, t, J=5.8 Hz), 3.61 (4H, t, J=5.6 Hz), 3.94 (2H, s), 4.01 (2H, d, J=7.3 Hz), 7.39 (2H, d, J=8.6 Hz), 7.81 (2H, d, J=8.6 Hz), 8.14 (1H, s).

IR (KBr) cm⁻¹: 3344, 2927, 1659, 1611, 1402, 1049, 721.

Mass m/z: 360 (M⁺−CH₂OH).

Example 160 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 73.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.29-2.41 (1H, m), 2.36 (6H, s), 2.52 (3H, s), 3.52 (2H, d, J=1.2 Hz), 4.07 (2H, d, J=7.4 Hz), 7.31 (2H, d, J=8.6 Hz), 7.77 (2H, d, J=8.4 Hz), 7.79 (1H, s).

Example 161 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethyl-aminomethyl-2-isobutyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 82.3%).

Melting point: 216.8-218.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.8 Hz), 2.23-2.36 (1H, m), 2.53 (3H, s), 2.82 (6H, s), 4.05 (2H, d, J=7.1 Hz), 4.27 (2H, s), 7.41 (2H, d, J=8.3 Hz), 7.84 (2H, d, J=8.3 Hz), 8.42 (1H, s).

IR (KBr) cm⁻¹: 3485, 1740, 1684, 1253, 856, 577.

Mass m/z: 331 (M⁺).

Example 162 Preparation of 2-isobutyl-6-[4-(methylthio)phenyl]-4-propargylaminomethyl-2H-pyridazin-3-one

Following the procedure of Example 1(10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one and propargylamine were reacted to yield the title compound as a yellow oil (yield: 52.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.26 (1H, t, J=2.3 Hz), 2.29-2.40 (1H, m), 2.52 (3H, s), 3.51 (2H, d, J=2.4 Hz), 3.90 (2H, s), 4.07 (2H, d, J=7.4 Hz), 7.31 (2H, d, J=8.4 Hz), 7.70 (1H, s), 7.73 (2H, d, J=8.4 Hz).

Example 163 Preparation of 2-isobutyl-6-[4-(methylthio)phenyl]-4-propargylaminomethyl-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-isobutyl-6-[4-(methylthio)phenyl]-4-propargylaminomethyl-2H-pyridazin-3-one was reacted to yield the title compound as a white solid (yield: 73.6%).

Melting point: 197.5-198.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.23-2.36 (1H, m), 2.53 (3H, s), 3.48 (1H, t, J=2.4 Hz), 3.95 (2H, d, J=2.4 Hz), 4.03 (2H, d, J=7.1 Hz), 4.17 (2H, s), 7.41 (2H, d, J=8.3 Hz), 7.82 (2H, d, J=8.6 Hz), 8.28 (1H, s).

IR (KBr) cm⁻¹: 3447, 3207, 2958, 2122, 1651, 1607, 1441, 1093.

Mass m/z: 341 (M⁺).

Example 164 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one 1) Preparation of 2-cyclopropylmethyl-4-methanesulfonyloxy-methyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one

To a solution of 2-cyclopropylmethyl-4-methane-sulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one (300 mg, 0.79 mmol) in methylene chloride (10 mL) was added dropwise at −20° C. a solution of 3-chloroperbenzoic acid (204 mg, 1.12 mmol) in methylene chloride (2 mL), and at the same temperature, the mixture was stirred for 30 minutes. A 10% aqueous sodium hydrogensulfite was added to the reaction mixture, and then, the mixture was extracted with chloroform. The extract was successively washed with a saturated aqueous sodium hydrogencarbonate and brine, and was then dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was recrystallized from chloroform-hexane to yield the title compound as a colorless crystalline powder (139 mg, 44.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.48-0.63 (4H, m), 1.37-1.46 (1H, m), 2.77 (3H, s), 3.18 (3H, s), 4.14 (2H, d, J=7.3 Hz), 5.30 (2H, d, J=1.4 Hz), 7.76 (2H, d, J=8.6 Hz), 7.84 (1H, t, J=1.4 Hz), 7.98 (2H, d, J=8.8 Hz).

Mass m/z: 396 (M⁺).

2) Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropyl-4-methanesulfonyloxymethyl-6-[4-(methyl-sulfinyl)phenyl]-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 60.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.46-0.60 (4H, m), 1.37-1.49 (1H, m), 2.34 (3H, s), 2.54 (4H, br), 2.64 (4H, br), 2.78 (3H, s), 3.61 (2H, s), 4.13 (2H, d, J=7.2 Hz), 7.75 (2H, d, J=8.2 Hz), 7.84 (1H, s), 7.99 (2H, d, J=8.2 Hz).

Example 165 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methyl-sulfinyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 64.3%).

Melting point: 80° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.41-0.57 (4H, m), 1.30-1.41 (1H, m), 2.76 (3H, s), 2.77 (3H, s), 3.01 (4H, br), 3.31 (4H, br), 3.77 (2H, s), 4.08 (2H, d, J=6.8 Hz), 7.80 (2H, d, J=8.3 Hz), 8.05-8.09 (3H, m).

IR (KBr) cm⁻¹: 3430, 3005, 1652, 1607, 1458, 1401, 1010, 838.

Mass m/z: 400 (M⁺).

Example 166 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one 1) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 164 (1), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 54.3%).

¹H NMR (400 MHz, CDCl₃) δ: 1.00 (6H, d, J=6.8 Hz), 2.29-2.41 (1H, m), 2.77 (3H, s), 3.18 (3H, s), 4.11 (2H, d, J=7.3 Hz), 5.29 (2H, d, J=1.5 Hz), 7.76 (2H, d, J=8.8 Hz), 7.83 (1H, t, J=1.2 Hz), 7.98 (2H, d, J=8.6 Hz).

Mass m/z: 398 (M⁺).

2) Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 61.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.30-2.41 (1H, m), 2.34 (3H, s), 2.54 (4H, br), 2.64 (4H, br), 2.77 (3H, s), 3.60 (2H, s), 4.10 (2H, d, J=7.4 Hz), 7.75 (2H, d, J=8.2 Hz), 7.82 (1H, s), 7.99 (2H, d, J=8.2 Hz).

Example 167 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfinyl)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 76.1%).

Melting point: 224.5-229.1° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.6 Hz), 2.22-2.35 (1H, m), 2.76 (3H, s), 2.77 (3H, s), 3.14 (4H, br), 3.35 (4H, br), 3.87 (2H, s), 4.04 (2H, d, J=7.1 Hz), 7.80 (2H, d, J=8.3 Hz), 8.07 (2H, d, J=8.3 Hz), 8.18 (1H, s).

IR (KBr) cm⁻¹: 3426, 2960, 1656, 1608, 1459, 1400, 1044, 1011.

Mass m/z: 402 (M⁺).

Example 168 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 46.2%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.30-2.43 (1H, m), 2.38 (6H, s), 2.76 (3H, s), 3.54 (2H, s), 4.10 (2H, d, J=7.4 Hz), 7.74 (2H, d, J=8.2 Hz), 7.87 (1H, s), 8.02 (2H, d, J=8.2 Hz).

Example 169 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfinyl)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfinyl)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 77.4%).

Melting point: 204.2-206.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.6 Hz), 2.24-2.36 (1H, m), 2.78 (3H, s), 2.83 (6H, s), 4.07 (2H, d, J=7.1 Hz), 4.28 (2H, s), 7.82 (2H, d, J=8.3 Hz), 8.09 (2H, d, J=8.3 Hz), 8.49 (1H, s).

IR (KBr) cm⁻¹: 3438, 2961, 1652, 1607, 1467, 1400, 1047.

Mass m/z: 347 (M⁺).

Example 170 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one 1) Preparation of 2-cyclopropylmethyl-4-methanesulfonyloxy-methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

To a solution of 2-cyclopropylmethyl-4-methane-sulfonyloxymethyl-6-[4-(methylthio)phenyl]-2H-pyridazin-3-one (226 mg, 0.59 mmol) in methylene chloride (10 mL) was added dropwise at −20° C. a solution of 3-chloroperbenzoic acid (410 mg, 2.38 mmol) in methylene chloride (2 mL), and at the same temperature, the mixture was stirred for 30 minutes. A 10% aqueous sodium hydrogensulfite was added to the reaction mixture, and then, the mixture was extracted with chloroform. The extract was successively washed with a saturated aqueous sodium hydrogencarbonate and brine, and was then dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was recrystallized from chloroform-hexane to yield the title compound as a colorless crystalline powder (209 mg, 85.3%).

¹H NMR (400 MHz, CDCl₃) δ: 0.46-0.63 (4H, m), 1.37-1.46 (1H, m), 3.10 (3H, s), 3.18 (3H, s), 4.20 (2H, d, J=7.3 Hz), 5.31 (2H, d, J=1.2 Hz), 7.86 (1H, t, J=1.2 Hz), 8.02 (2H, d, J=8.8 Hz), 8.06 (2H, d, J=9.0 Hz).

Mass m/z: 412 (M⁻).

2) Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropyl-4-methanesulfonyloxymethyl-6-[4-(methyl-sulfonyl)phenyl]-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 80.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.46-0.61 (4H, m), 1.38-1.48 (1H, m), 2.34 (3H, s), 2.54 (4H, br), 2.64 (4H, br), 3.10 (3H, s), 3.61 (2H, d, J=1.2 Hz), 4.13 (2H, d, J=7.1 Hz), 7.85 (1H, t, J=1.2 Hz), 8.03 (2H, d, J=9.0 Hz), 8.05 (2H, d, J=9.0 Hz).

Example 171 Preparation of 2-cyclopropylmethyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methyl-sulfonyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 76.8%).

Melting point: 209.0-211.4° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.41-0.46 (2H, m), 0.52-0.57 (2H, m), 1.31-1.41 (1H, m), 2.77 (3H, s), 3.04 (4H, br), 3.21 (3H, s), 3.31 (4H, br), 3.80 (2H, s), 4.09 (2H, d, J=7.1 Hz), 8.04 (2H, d, J=8.3 Hz), 8.12 (1H, s), 8.14 (2H, d, J=8.3 Hz).

IR (KBr) cm⁻¹: 3434, 3012, 1652, 1596, 1458, 1402, 1302, 1150.

Mass m/z: 416 (M⁺).

Example 172 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-4-methanesulfonyloxymethyl-6-[4-(methyl-sulfonyl)phenyl]-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 65.6%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.62 (4H, m), 1.39-1.49 (1H, m), 2.38 (6H, s), 3.09 (3H, s), 3.55 (2H, s), 4.14 (2H, d, J=7.2 Hz), 7.89 (1H, s), 8.02 (2H, d, J=8.4 Hz), 8.06 (2H, d, J=8.6 Hz).

Example 173 Preparation of 2-cyclopropylmethyl-4-dimethylamino-methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-cyclopropyl-methyl-4-dimethylaminomethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 63.4%).

Melting point: 239.5-240.7° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.43-0.59 (4H, m), 1.33-1.43 (1H, m), 2.83 (6H, s), 3.23 (3H, s), 4.13 (2H, d, J=7.1 Hz), 4.29 (2H, s), 8.06 (2H, d, J=7.8 Hz), 8.17 (2H, d, J=8.3 Hz), 8.57 (1H, s).

IR (KBr) cm⁻¹: 3447, 2674, 1646, 1608, 1596, 1306, 1150, 777.

Mass m/z: 361 (M⁺).

Example 174 Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-[4-(methyl-sulfonyl)phenyl]-2H-pyridazin-3-one 1) Preparation of 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 170 (1), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylthio)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 97.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.29-2.41 (1H, m), 3.10 (3H, s), 3.18 (3H, s), 4.12 (2H, d, J=7.3 Hz), 5.29 (2H, d, J=1.2 Hz), 7.85 (1H, t, J=1.4 Hz), 8.02 (2H, d, J=8.8 Hz), 8.05 (2H, d, J=8.8 Hz).

Mass m/z: 414 (M⁺).

2) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)-methyl-2-isobutyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 75.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 1.47 (9H, s), 2.29-2.41 (1H, m), 2.54 (4H, br), 3.09 (3H, s), 3.51 (4H, br), 3.60 (2H, s), 4.11 (2H, d, J=7.2 Hz), 7.86 (1H, s), 8.02 (2H, d, J=8.8 Hz), 8.05 (2H, d, J=8.8 Hz).

Example 175 Preparation of 2-isobutyl-6-[4-(methylsulfonyl)-phenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 2, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-isobutyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 88.2%).

Melting point: 222.4-224.2° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.96 (6H, d, J=6.8 Hz), 2.22-2.35 (1H, m), 3.06 (4H, br), 3.21 (3H, s), 3.28 (4H, t, J=5.2 Hz), 3.87 (2H, s), 4.05 (2H, d, J=7.1 Hz), 8.04 (2H, d, J=8.6 Hz), 8.14 (2H, d, J=8.3 Hz), 8.22 (1H, s).

IR (KBr) cm⁻¹: 3421, 2957, 1656, 1611, 1597, 1305, 1149, 961.

Mass m/z: 404 (M⁺).

Example 176 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 88.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.8 Hz), 2.28-2.40 (1H, m), 2.37 (3H, s), 2.53 (4H, br), 2.63 (4H, br), 3.10 (3H, s), 3.60 (2H, s), 4.10 (2H, d, J=7.3 Hz), 7.84 (1H, s), 8.02 (2H, d, J=9.0 Hz), 8.05 (2H, d, J=8.8 Hz).

Example 177 Preparation of 2-isobutyl-4-(4-methyl-1-piperazinyl)-methyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-isobutyl-4-(4-methyl-1-piperazinyl)methyl-6-[4-(methylsulfonyl)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 62.0%).

Melting point: 224.5-228.0° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.95 (6H, d, J=6.8 Hz), 2.23-2.35 (1H, m), 2.76 (3H, s), 3.08 (4H, br), 3.21 (3H, s), 3.32 (4H, br), 3.83 (2H, s), 4.05 (2H, d, J=7.1 Hz), 8.04 (2H, d, J=8.3 Hz), 8.13 (2H, d, J=8.5 Hz), 8.15 (1H, s).

IR (KBr) cm⁻¹: 3447, 2958, 1652, 1610, 1596, 1319,. 1152, 955.

Mass m/z: 418 (M⁺).

Example 178 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-isobutyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 51.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.98 (6H, d, J=6.6 Hz), 2.28-2.40 (1H, m), 2.73 (4H, t, J=4.8 Hz), 3.08 (3H, s), 3.68 (4H, t, J=4.9 Hz), 3.73 (2H, s), 4.11 (2H, d, J=7.4 Hz), 7.93 (1H, s), 8.00 (2H, d, J=8.6 Hz), 8.05 (2H, d, J=8.8 Hz).

Mass m/z: 392 (M⁺−CH₂OH).

Example 179 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one

Following the procedure of Example 7, 2-isobutyl-4-methanesulfonyloxymethyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 82.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.99 (6H, d, J=6.6 Hz), 2.30-2.41 (1H, m), 2.37 (6H, s), 3.09 (3H, s), 3.52 (2H, s), 4.11 (2H, d, J=7.2 Hz), 7.86 (1H, s), 8.02 (2H, d, J=8.8 Hz), 8.05 (2H, d, J=8.8 Hz).

Example 180 Preparation of 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfonyl)phenyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-dimethylaminomethyl-2-isobutyl-6-[4-(methylsulfonyl)-phenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 58.6%).

Melting point: 221.4-223.3° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.97 (6H, d, J=6.6 Hz), 2.25-2.36 (1H, m), 2.82 (6H, s), 3.22 (3H, s), 4.08 (2H, d, J=7.3 Hz), 4.28 (2H, s), 8.06 (2H, d, J=8.3 Hz), 8.15 (2H, d, J=8.5 Hz), 8.55 (1H, s).

IR (KBr) cm⁻¹: 3447, 2963, 1653, 1609, 1597, 1307, 1152, 777.

Mass m/z: 363 (M⁺).

Example 181 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-pyrrolidinomethyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and pyrrolidine were reacted to yield the title compound as a yellow oil (yield: 75.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.61 (4H, m), 1.42 (1H, m), 1.85-2.00 (4H, m), 2.70-3.00 (4H, m), 3.83 (2H, brs), 3.94 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.60 (1H, d, J=8.5 Hz), 7.65 (1H, dd, J=8.5, 2.0 Hz), 8.00 (1H, brs).

IR (Neat) cm⁻¹: 1652, 1608, 1523, 1438, 1286, 758.

Mass m/z: 357 (M⁺).

Example 182 Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and cyclopentylmethyl bromide {J. Org. Chem., 36, 3103 (1971)) were reacted to yield the title compound as yellow needles (yield: 72.0%).

Melting point: 56-66° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.30-1.45 (2H, m), 1.53-1.65 (2H, m), 1.65-1.80 (4H, m), 2.57 (1H, m), 3.95 (3H, s), 3.98 (3H, s), 4.24 (2H, d, J=7.8 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.50 (1H, d, J=8.8 Hz), 7.61 (1H, d, J=10.2 Hz), 8.19 (1H, s).

2) Preparation of 4-carboxy-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 71.1%).

Melting point: 159-161° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.33-1.45 (2H, m), 1.58-1.65 (2H, m), 1.68-1.82 (4H, m), 2.57 (1H, m), 3.97 (3H, s), 4.32 (2H, d, J=7.6 Hz), 7.06 (1H, dd, J=8.5, 8.5 Hz), 7.56 (1H, d, J=8.5 Hz), 7.68 (1H, dd, J=12.2, 2.0 Hz), 8.61 (1H, s).

3) Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 47.3%).

Melting point: 130-133° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.30-1.42 (2H, m), 1.50-1.62 (2H, m), 1.62-1.80 (4H, m), 2.54 (1H, m), 3.95 (3H, s), 4.19 (2H, d, J=7.6 Hz), 4.71 (2H, s), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.51 (1H, d, J=8.5 Hz), 7.62 (1H, dd, J=12.8, 1.5 Hz), 7.63 (1H, s).

4) Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 75.3%).

Melting point: 108-116° C.

¹H NMR (400 MHz, CDCl₃) δ: 1.25-1.32 (2H, m), 1.32-1.45 (2H, m), 1.65-1.77 (4H, m), 2.54 (1H, m), 3.17 (3H, s), 3.95 (3H, s), 4.19 (2H, d, J=7.6 Hz), 5.27 (2H, s), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.50 (1H, d, J=8.5 Hz), 7.62 (1H, dd, J=12.2, 2.2 Hz), 7.74 (1H, s).

5) Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 61.4%).

¹H NMR (400 MHz, CDCl₃) δ: 1.32-1.42 (2H, m), 1.50-1.60 (2H, m), 1.65-1.80 (4H, m), 2.38, 2.40 (each s, 3H in total), 2.54 (1H, m), 2.60-2.75 (8H, m), 3.59 (2H, s), 3.95 (3H, s), 4.18 (2H, d, J=7.6 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.54 (1H, d, J=8.5 Hz), 7.61 (1H, dd, J=8.5, 2.2 Hz), 7.72 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1523, 1439, 1286, 760.

Mass m/z: 414 (M⁺).

Example 183 Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale brown crystalline powder (yield: 59.6%).

Melting point: 234-236° C. (dec.)

¹H NMR (400 MHz, DMSO-d₆) δ: 1.28-1.40 (2H, m), 1.48-1.56 (2H, m), 1.60-1.73 (4H, m), 2.46 (1H, m), 2.82 (3H, s), 3.50-3.75 (10H, m), 3.91 (3H, s), 4.10 (2H, d, J=7.6 Hz), 7.31 (1H, dd, J=8.8, 8.8 Hz), 7.68-7.76 (2H, m), 8.25 (1H, s).

IR (KBr) cm⁻¹: 1652, 1606, 1523, 1439, 1292, 764.

Example 184 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 54.9%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30-1.45 (2H, m), 1.50-1.62 (2H, m), 1.62-1.80 (4H, m), 2.53 (1H, m), 2.75-2.90 (4H, m), 3.70-3.75 (4H, m), 3.80-3.85 (2H, m), 3.94 (3H, s), 4.20 (2H, d, J=7.6 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.56 (1H, d, J=8.5 Hz), 7.63 (1H, dd, J=8.5, 2.0 Hz), 7.65 (1H, m).

IR (Neat) cm⁻¹: 1648, 1598, 1523, 1439, 1267, 728.

Mass m/z: 383 (M⁺−2H₂O).

Example 185 Preparation of 2-cyclopentylmethyl-4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow oil (yield: 63.7%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30-1.45 (2H, m), 1.50-1.63 (2H, m), 1.63-1.80 (4H, m), 2.43 (6H, s), 2.55 (1H, m), 3.61 (2H, s), 3.94 (3H, s), 4.19 (2H, d, J=7.6 Hz), 7.20 (1H, dd, J=8.5, 8.5 Hz), 7.58 (1H, d, J=8.5 Hz), 7.65 (1H, dd, J=8.5, 2.2 Hz), 7.91 (1H, brs).

IR (Neat) cm⁻¹: 1652, 1608, 1523, 1438, 1288, 762.

Mass m/z: 359 (M⁺).

Example 186 Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H- pyridazin-3-one 1) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 78.8%).

¹H NMR (400 MHz, CDCl₃) δ: 1.35-1.43 (2H, m), 1.47 (9H, s), 1.55-1.60 (2H, m), 1.65-1.75 (4H, m), 2.45-2.60 (5H, m), 3.45-3.55 (4H, m), 3.95 (3H, s), 4.18 (2H, d, J=7.6 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.52 (1H, m), 7.62 (1H, d, J=12.4 Hz), 7.74 (1H, m).

2) Preparation of 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 20, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 88.0%).

¹H NMR (400 MHz, CDCl₃) δ: 1.33-1.43 (2H, m), 1.50-1.62 (2H, m), 1.62-1.80 (4H, m), 2.55 (1H, m), 2.57-2.63 (4H, m), 3.00-3.02 (4H, m), 3.56 (2H, brs), 3.95 (3H,s), 4.18 (2H, d, J=7.6 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.52 (1H, d, J=8.5 Hz), 7.62 (1H, dd, J=8.5, 2.2 Hz), 7.73 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1523, 1439, 1287, 761.

Mass m/z: 400 (M⁺).

Example 187 Preparation of 4-aminomethyl-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield a crude product. Without purification, the crude product was reacted further in accordance with the procedure of Example 24 (2) to yield the title compound as a yellow oil (yield: 53.7%).

¹H NMR (400 MHz, CDCl₃) δ: 1.30-1.45 (2H, m), 1.50-1.63 (2H, m), 1.63-1.80 (4H, m), 2.54 (1H, m), 3.91 (2H, s), 3.93 (3H, s), 4.17 (2H, d, J=7.6 Hz), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.52 (1H, d, J=8.5 Hz), 7.62 (1H, dd, J=8.5, 2.2 Hz), 7.71 (1H, brs).

IR (Neat) cm⁻¹: 3376, 1649, 1606, 1523, 1439, 1285, 761.

Mass m/z: 331 (M⁺).

Example 188 Preparation of 4-aminomethyl-2-cyclopentylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-2-cyclopentylmethyl-6-(³-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 59.0%).

Melting point: 193-196° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 1.29-1.40 (2H, m), 1.45-1.57 (2H, m), 1.60-1.70 (4H, m), 2.45 (1H, m), 3.91 (3H, s), 4.00 (2H, s), 4.12 (2H, d, J=7.6 Hz), 7.34 (1H, dd, J=8.5, 8.5 Hz), 7.69-7.72 (2H, m), 8.47 (1H, brs).

IR (KBr) cm⁻¹: 3436, 1656, 1617, 1521, 1438, 1295, 763.

Example 189 Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and 4-fluorobenzyl chloride were reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 86.6%).

¹H NMR (400 MHz, CDCl₃) δ: 3.95 (3H, s), 3.97 (3H, s), 5.39 (2H, s), 7.00-7.06 (3H, m), 7.48-7.63 (4H, m), 8.19 (1H, s).

2) Preparation of 4-carboxy-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 97.7%).

Melting point: 222-224° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.97 (3H, s), 5.47 (2H, s), 7.03-7.10 (3H, m), 7.49-7.56 (3H, m), 7.67 (1H, dd, J=12.1, 2.2 Hz), 8.60 (1H, s).

3) Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 27.0%).

Melting point: 127-130° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.95 (3H, s), 4.79 (2H, d, J=1.5 Hz), 5.36 (2H, s), 6.98-7.05 (3H, m), 7.46-7.52 (3H, m), 7.61 (1H, dd, J=12.2, 2.2 Hz), 7.65 (1H, s).

4) Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow powder (yield: 49.4%).

Melting point: 125-133° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.15 (3H, s), 3.95 (3H, s), 5.25 (2H, d, J=1.2 Hz), 5.35 (2H, s), 7.00-7.06 (3H, m), 7.45-7.55 (3H, m), 7.61 (1H, dd, J=12.4, 2.2 Hz), 7.74 (1H, s).

5) Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiprazine were reacted to yield the title compound as a slightly-brown crystalline powder (yield: 45.8%).

Melting point: 112-113° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.39 (3H, s), 2.60-2.90 (8H, m), 3.60 (2H, s), 3.95 (3H, s), 5.34 (2H, s), 6.99-7.06 (3H, m), 7.47-7.51 (3H, m), 7.59 (1H, dd, J=12.4, 2.0 Hz), 7.71 (1H, s).

IR (KBr) cm⁻¹: 1651, 1608, 1518, 1439, 1289, 764.

Mass m/z: 440 (M⁺).

Example 190 Preparation of 4-dimethylaminomethyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 60.8%).

Melting point: 127-129° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.41 (6H, s), 3.58 (2H, s), 3.94 (3H, s), 5.35 (2H, s), 6.98-7.05 (3H, m), 7.46-7.52 (2H, m), 7.56 (1H, d, J=8.8 Hz), 7.64 (1H, dd, J=12.4, 2.2 Hz), 7.90 (1H, brs).

IR (KBr) cm⁻¹: 1652, 1612, 1519, 1439, 1291, 763.

Mass m/z: 385 (M⁺).

Example 191 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 66.1%).

¹H NMR (400 MHz, CDCl₃) δ: 2.70-2.92 (4H, m), 3.70-3.85 (6H, m), 3.93 (3H, s), 5.35 (2H, s), 6.99-7.04 (3H, m), 7.45-7.50 (2H, m), 7.55 (1H, d, J=8.3 Hz), 7.63 (1H, dd, J=12.4, 2.0 Hz), 7.90 (1H, m).

IR (Neat) cm⁻¹: 1652, 1606, 1520, 1435, 1281, 762.

Mass m/z: 385 (M⁺−CH₂OH).

Example 192 Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 78.8%).

¹H NMR (400 MHz, CDCl₃) δ: 1.46 (9H, s), 1.55-1.65 (4H, m), 3.40-3.60 (4H, m), 3.95 (3H, s), 5.34 (2H, s), 6.96-7.05 (3H, m), 7.47-7.50 (3H, m), 7.41 (1H, d, J=12.4 Hz), 7.74 (1H, brs).

2) Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 20, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 63.4%).

Melting point: 142-143° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.50-2.60 (4H, m), 2.96-3.02 (4H, m), 3.54 (2H, d, J=1.2 Hz), 3.95 (3H, s), 5.34 (2H, s), 6.98-7.06 (3H, m), 7.46-7.53 (3H, m), 7.61 (1H, dd, J=12.5, 2.2 Hz), 7.74 (1H, br.s).

IR (KBr) cm⁻¹: 1652, 1609, 1523, 1437, 1290, 762.

Mass m/z: 426 (M⁺).

Example 193 Preparation of 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(1-piperazinyl)methyl-2H-pyridazin-3-one was reacted to yield the title compound as a colorless crystalline powder (yield: 76.9%).

Melting point: 153-156° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 3.30-3.75 (10H, m), 3.90 (3H, s), 5.33 (2H, s), 7.15-7.21 (2H, m), 7.30 (1H, m), 7.43-7.49 (2H, m), 7.69-7.78 (3H, m).

IR (KBr) cm⁻¹: 1660, 1609, 1524, 1439, 1292, 766.

Example 194 Preparation of 4-aminomethyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield a crude product. Without purification, the crude product was reacted further in accordance with the procedure of Example 24 (2) to yield the title compound as a pale brown crystalline powder (yield: 50.4%).

Melting point: 145-149° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.92 (3H, s), 3.94 (2H, s), 5.31 (2H, s), 6.95-7.03 (3H, m), 7.40-7.52 (3H, m), 7.60 (1H, dd, J=12.5, 2.2 Hz), 7.75 (1H, brs)

IR (KBr) cm⁻¹: 3391, 1648, 1606, 1519, 1437, 1292, 761.

Mass m/z: 357 (M⁺).

Example 195 Preparation of 4-aminomethyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-2-(4-fluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 72.5%).

Melting point: 210-214° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 3.91 (3H, s), 4.01 (2H, s), 5.35 (2H, s), 7.16-7.21 (2H, m), 7.34 (1H, dd, J=8.8, 8.8 Hz), 7.45-7.49 (2H, m), 7.68-7.78 (2H, m), 8.29 (1H, s).

IR (KBr) cm⁻¹: 3429, 1653, 1612, 1522, 1439, 1292, 764.

Example 196 Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and the mesylate derivative of 3-(4-fluorophenyl)-1-propanol {J. Med. Chem., 19, 461 (1976) were reacted to yield the title compound as a yellow oil (yield: 90.1%). The mesylate derivative was prepared in accordance with the procedure of Example 1 (9).

¹H NMR (400 MHz, CDCl₃) δ: 2.16-2.26 (2H, m), 2.71 (2H, t, J=7.3 Hz), 3.95 (3H, s), 3.98 (3H, s), 4.32 (2H, t, J=7.3 Hz), 6.93-7.06 (3H, m), 7.14-7.18 (2H, m), 7.49 (1H, m), 7.60 (1H, dd, J=13.2, 2.2 Hz), 8.17 (1H, s).

2) Preparation of 4-carboxy-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 89.2%).

Melting point: 185-187° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.20-2.30 (2H, m), 2.74 (2H, t, J=7.3 Hz), 3.97 (3H, s), 4.40 (2H, t, J=7.3 Hz), 6.94-7.17 (5H, m), 7.55 (1H, d, J=8.5 Hz), 7.66 (1H, dd, J=12.2, 2.2 Hz), 8.58 (1H, s).

3) Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 37.0%).

Melting point: 130-133° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.15-2.22 (2H, m), 2.71 (2H, t, J=7.3 Hz), 3.95 (3H, s), 4. 27 (2H, t, J=7.3 Hz), 4.70 (2H, d, J=1.2 Hz), 6.93-7.06 (3H, m), 7.14-7.18 (2H, m), 7.50 (1H, d, J=8.8 Hz), 7.61 (1H, dd, J=12.7, 2.2 Hz), 7.63 (1H, s).

4) Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow powder (yield: 92.3%).

Melting point: 112-116° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.15-2.25 (2H, m), 2.71 (2H, t, J=7.3 Hz), 3.1 7 (3H, s), 3.95 (3H, s) ,4.27 (2H, t, J=7.3 Hz), 5.25 (2H, d, J=1.2 Hz), 6.93-7.05 (3H, m), 7.14-7.18 (2H, m), 7.49 (1H, d, J=8.5 Hz), 7.61 (1H, dd, J=13.4, 2.0 Hz), 7.72 (1H, s).

5) Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 79.3%).

¹H NMR (400 MHz, CDCl₃) δ: 2.15-2.25 (2H, m), 2.41 (3H, s), 2.60-2.75 (10H, m), 3.58 (2H, s), 3.75 (3H, s), 4.27 (2H, t, J=7.3 Hz), 6.92-7.06 (3H, m), 7.14-7.18 (2H, m), 7.51 (1H, d, J=8.5 Hz), 7.60 (1H, dd, J=12.4, 2.0 Hz), 7.69 (1H, s).

IR (Neat) cm⁻¹: 1652, 1608, 1511, 1439, 1284, 758.

Mass m/z: 468 (M⁺).

Example 197 Preparation of 4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 7, 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a pale yellow crystalline powder (yield: 61.8%).

Melting point: 97-100° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.15-2.25 (2H, m), 2.43 (6H, s), 2.71 (2H, t, J=7.3 Hz), 3.60 (2H, s), 3.94 (3H, s), 4.27 (2H, t, J=7.3 Hz), 6.93-7.05 (3H, m), 7.15-7.18 (2H, m), 7.57 (1H, d, J=8.5 Hz), 7.64 (1H, dd, J=12.6, 2.2 Hz), 7.90 (1H, brs).

IR (KBr) cm⁻¹: 1653, 1611, 1510, 1436, 1296, 763.

Mass m/z: 413 (M⁺).

Example 198 Preparation of 4-N,N-bis(2-hydroxyethyl)aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 67.3%).

¹H NMR (400 MHz, CDCl₃) δ: 2.14-2.22 (2H, m), 2.70 (2H, t, J=7.6 Hz), 2.75-2.95 (4H, m), 3.70-3.80 (6H, m), 3.94 (3H, s), 4.28 (2H, t, J=7.6 Hz), 6.93-7.05 (3H, m), 7.15-7.18 (2H, m), 7.56 (1H, m), 7.63 (1H, m), 7.85 (1H, m).

IR (Neat) cm⁻¹: 1645, 1601, 1510, 1439, 1277, 763.

Mass m/z: 473 (M⁺).

Example 199 Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-(1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 72.6%).

¹H NMR (400 MHz, CDCl₃) δ: 1.40 (9H, s), 2.07-2.16 (2H, m), 2.40-2.50 (4H, m), 2.63 (2H, t, J=7.6 Hz), 3.36-3.46 (4H, m) 3.48 (2H, brs), 3.88 (3H, s), 4.20 (2H, t, J=7.6 Hz), 6.84-6.98 (3H, m), 7.07-7.11 (2H, m), 7.43 (1H, d, J=8.1 Hz), 7.53 (1H, d, J=12.4 Hz), 7.65 (1H, brs).

2) Preparation of 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-(1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 20, 4-(4-tert-butoxycarbonyl-1-piperazinyl)methyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 97.2%).

¹H NMR (400 MHz, CDCl₃) δ: 2.12-2.22 (2H, m), 2.50-2.60 (4H, m), 2.71 (2H, t, J=7.3 Hz), 2.92-3.02 (4H, m), 3.53 (2H, s), 3.95 (3H, s), 4.27 (2H, t, J=7.3 Hz), 6.91-7.06 (3H, m), 7.15-7.18 (2H, m), 7.51 (1H, d, J=8.8 Hz), 7.61 (1H, dd, J=12.5, 2.2 Hz), 7.73 (1H, s).

IR (Neat) cm⁻¹: 1650, 1607, 1510, 1439, 1275, 758.

Mass m/z: 454 (M⁺).

Example 200 Preparation of 4-aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to a crude product. Without purification, the crude product was reacted in accordance with the procedure of Example 24 (2) to yield the title compound as a pale yellow crystalline powder (yield: 41.7%).

Melting point: 82-84° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.12-2.22 (2H, m), 2.70 (2H, t, J=7.6 Hz), 3.89 (2H, s), 3.94 (3H, s), 4.27 (2H, t, J=7.6 Hz), 6.93-7.04 (3H, m), 7.15-7.18 (2H, m), 7.51 (1H, d, J=7.3 Hz), 7.61 (1H, dd, J=12.4, 2.0 Hz), 7.67 (1H, s).

IR (KBr) cm⁻¹: 3366, 1651, 1605, 1509, 1436, 1273, 764.

Mass m/z: 385 (M⁺).

Example 201 Preparation of 4-aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-6-(3-fluoro-4-methoxyphenyl)-2-[3-(4-fluorophenyl)propyl]-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 73.1%).

Melting point: 160-165° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 2.05-2.15 (2H,m), 2.66 (2H, t, J=7.3 Hz), 3.92 (3H, s), 3.99 (2H, s), 4.19 (2H, t, J=7.3 Hz), 7.05-7.12 (2H, m), 7.23-7.30 (2H, m), 7.34 (1H, dd, J=8.8, 8.8 Hz), 7.66-7.76 (2H, m), 8.25 (1H, s).

IR (KBr) cm⁻¹: 3430, 1652, 1515, 1436, 1269, 763.

Example 202 Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and 4-chlorobenzyl chloride were reacted to yield the title compound as yellow needles (yield: 97.6%).

Melting point: 170.5-171.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.95 (3H, s), 3.99 (3H, s), 5.38 ((2H, s), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.31 (2H, d, J=8.5 Hz), 7.47 (2H, d, J=8.5 Hz), 7.49 (1H, m), 7.60 (1H, dd, J=12.2, 2.2 Hz), 8.20 (1H, s)

IR (KBr) cm⁻¹: 1723, 1670, 1526, 1271, 1128.

Mass m/z: 402 (M⁺), 404 ((M⁺).

2) Preparation of 4-carboxy-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 96.0%).

Melting point: 228.3-229.1° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.97 (3H, s), 5.46 (2H, s), 7.07 (1H, dd, J=8.5, 8.5 Hz), 7.35 (2H, d, J=8.3 Hz), 7.46 (2H, d, J=8.3 Hz), 7.55 (1H, d, J=8.4 Hz), 7.67 (1H, dd, J=12.2, 2.2 Hz), 8.61 (1H, s).

IR (KBr) cm⁻¹: 1745, 1635, 1456, 1447, 1431, 1298, 1273.

Mass m/z: 388 (M⁺), 390 (M⁺).

3) Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (yield: 20.4%).

Melting point: 164.6-165.3° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.94 (3H, s), 4.69 (2H, s), 5.34 (2H, s), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.30 (2H, d, J=8.5 Hz), 7.42 (2H, d, J=8.5 Hz), 7.50 (1H, m), 7.63 (1H, dd, J=12.4, 2.2 Hz), 7.67 (1H, s).

IR (KBr) cm⁻¹: 3373, 1653, 1610, 1527, 1291, 1135.

Mass m/z: 374 (M⁺), 376 (M⁺).

4) Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow needles (yield: 81.6%).

Melting point: 156.5-157.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.15 (3H, s), 3.95 (3H, s), 5.22 (2H, d, J=1.5 Hz), 5.35 (2H, s), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.31 (2H, d, J=8.5 Hz), 7.42 (2H, d, J=8.5 Hz), 7.49 (1H, m), 7.61 (1H, dd, J=12.2, 2.2 Hz), 7.75 (1H, s).

IR (KBr) cm⁻¹: 1658, 1616, 1358, 1183, 1017.

5) Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as pale brown prisms (yield: 39.5%).

Melting point: 128.7-130.2° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.52 (4H, brs), 2.60 (4H, brs), 3.55 (2H, s), 3.95 (3H, s), 5.34 (2H, s), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.30 (2H, d, J=8.5 Hz), 7.43 (2H, d, J=8.5 Hz), 7.51 (1H, m), 7.60 (1H, dd, J=12.4, 2.0 Hz), 7.73 (1H, s).

IR (KBr) cm⁻¹: 1652, 1607, 1524, 1516, 1438, 1288, 1135.

Example 203 Preparation of 2-(4-chlorobenzyl)-4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 74.7%).

Melting point: 95.3-96.7° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (6H,s), 3.47 (2H, d, J=1.2 Hz), 3.94 (3H, s), 5.34 (2H, s), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.30 (2H, d, J=8.5 Hz), 7.44 (2H, d, J=8.5 Hz), 7.53 (1H, ddd, J=8.5, 2.0, 1.2 Hz), 7.62 (1H, dd, J=12.4, 2.2 Hz), 7.74 (1H, s).

IR (KBr) cm⁻¹: 1652, 1609, 1524, 1515, 1436, 1289, 1264, 1017.

Mass m/z: 401 (M⁺), 403 (M⁺).

Example 204 Preparation of 2-(4-chlorobenzyl)-4-dimethylaminomethyl-6-(3-fluoro-4-methyoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 2-(4-chlorobenzyl)-4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 59.7%).

Melting point: 193.4-194.7° C.

¹H NMR (400 MHz, CD₃OD) δ: 2.96 (6H, s), 3.94 (3H, s), 4.33 (2H, s), 5.43 (2H, s), 7.22 (1H, dd, J=8.5, 8.5Hz), 7.36 (2H, d, J=8.5 Hz), 7.46 (2H, d, J=8.5 Hz), 7.67-7.72 (2H, m), 8.20 (1H, s).

IR (KBr) cm⁻¹: 1655, 1616, 1529, 1327, 1279.

Example 205 Preparation of 4-aminomethyl-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one 1) Preparation of 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-phthalimidomethyl-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly-yellow needles (yield: 75.4%).

Melting point: 212.5-213.9° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.90 (3H, s), 4.88 (2H, d, J=0.73 Hz), 5.35 (2H, s), 6.95 (1H, dd, J=8.5, 8.5 Hz), 7.29 (1H, s), 7.31 (2H, d, J=8.5 Hz), 7.36 (1H, m), 7.44 (2H, d, J=8.5 Hz), 7.47 (1H, dd, J=12.2, 2.0 Hz), 7.76-7.81 (2H, m), 7.89-7.94 (2H, m).

IR (KBr) cm⁻¹: 1773, 1713, 1651, 1610, 1522, 1439, 1419, 1393, 1300.

Mass m/z: 503 (M⁺), 505 (M⁺).

2) Preparation of 4-aminomethyl-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 24 (2), 2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-phthalimidomethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly-yellow needles (yield: 48.8%).

Melting point: 128.5-131.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.88 (2H, s), 3,94 (3H, s), 5.34 (2H, s), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.30 (2H, d, J=8.5 Hz), 7.43 (2H, d, J=8.5 Hz), 7.51 (1H, ddd, J=8.5, 2.2, 1.2 Hz), 7.61 (1H, dd, J=12.4, 2.2 Hz), 7.69 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3392, 1615, 1604, 1520, 1434, 1292, 1133, 1018.

Mass m/z: 373 (M⁺), 375 ((M⁺).

Example 206 Preparation of 4-aminomethyl-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-aminomethyl-2-(4-chlorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 66.0%).

Melting point: 202.0-205.5° C.

¹H NMR (400 MHz, CD₃OD) δ: 3.94 (3H, s), 4.13 (2H, s), 5.41 (2H, s), 7.21 (1H, dd, J=8.8, 8.8 Hz), 7.35 (2H, d, J=8.5 Hz), 7.46 (2H, d, J=8.5 Hz), 7.65-7.71 (2H, m), 8.08 (1H. s).

IR (KBr) cm⁻¹: 2940, 1655, 1616, 1526, 1439, 1292.

Example 207 Preparation of 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and 3,4-difluorobenzyl bromide were reacted to yield the title compound as a yellow crystalline powder (yield: 92.1%)

Melting point: 144-148° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.96 (3H, s), 3.97 (3H, s), 5.35 (2H, s), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.12 (1H, m), 7.28 (1H, m), 7.36 (1H, m), 7.50 (1H, m), 7.60 (1H, dd, J=12.2, 1.5 Hz), 8.21 (1H, s).

IR (KBr) cm⁻¹: 1756, 1656, 1609, 1518, 1439, 1239, 1293, 1278, 1204.

Mass m/z: 404 (M⁺).

2) Preparation of 4-carboxy-2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a yellow crystalline powder (yield: 97.6%).

Melting point: 196.4-197.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.97 (3H, s), 5.44 (2H, s), 7.07 (1H, dd, J=8.5, 8.5 Hz), 7.17 (1H, m), 7.27 (1H, m), 7.36 (1H, ddd, J=8.1, 8.1, 2.2 Hz), 7.56 (1H, m), 7.66 (1H, dd, J=12.2, 2.2 Hz), 8.61 (1H, s), 13.83 (1H, s).

IR (KBr) cm⁻¹: 1757, 1636, 1567, 1518, 1463, 1440, 1284.

Mass m/z: 390 (M⁺).

3) Preparation of 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as slightly-yellow neeldes (yield: 7.7%).

Melting point: 154.1-155.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.85 (1H, t, J=5.6 Hz), 3.95 (3H, s), 4.71 (2H, d, J=5.6 Hz), 5.33 (2H, s), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.12 (1H, m), 7.23 (1H, m), 7.31 (1H, ddd, J=11.0, 7.6, 2.2 Hz), 7.51 (1H, ddd, J=8.5, 2.2, 1.2 Hz), 7.61 (1H, dd, J=12.4, 2.2 Hz), 7.68 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3390, 1648, 1602, 1518, 1440, 1285, 1141.

Mass m/z: 376 (M⁺).

4) Preparation of 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as slightly-yellow neeldes (yield: 91.5%).

Melting point: 145.6-146.6° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.16 (3H, s), 3.96 (3H, s), 5.26 (2H, d, J=1.2 Hz), 5.32 (2H, s), 7.04 (1H, dd, J=8.5 8.5 Hz), 7.13 (1H, m), 7.23 (1H, m), 7.32 (1H, m), 7.50 (1H, m), 7.61 (1H, dd, J=12.4, 2.2 Hz), 7.76 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 1656, 1612, 1522, 1440, 1352, 1277, 1163.

Mass m/z: 454 (M⁺).

5) Preparation of 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(3,4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as slightly-yellow neeldes (yield: 55.0%).

Melting point: 135.4-136.0° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.51 (4H, brs), 2.62 (4H, brs), 3.56 (2H, d, J=1.5 Hz), 3.95 (3H, s), 5.31 (2H, s), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.11 (1H, m), 7.23 (1H, m), 7.32 (1H, ddd, J=11.0, 7.6, 2.0 Hz), 7.52 (1H, ddd, J=8.5, 2.2, 1.2 Hz), 7.59 (1H, dd, J=12.2, 2.2 Hz), 7.74 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 1652, 1608, 1522, 1437, 1291, 1273, 1139.

Mass m/z: 458 (M⁺).

Example 208 Preparation of 2-(3,4-difluorobenzyl)-4-dimethylaminomethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-(3, 4-difluorobenzyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as slightly-yellow needles (yield: 77.1%).

Melting point: 129.9-130.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.35 (6H, s), 3.49 (2H, s), 3.95 (3H, s), 5.32 (2H, s), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.11 (1H, m), 7.24 (1H, m), 7.32 (1H, ddd, J=11.0, 7.6, 2.2 Hz), 7.54 (1H, ddd, J=8.5, 2.2, 1.2 Hz), 7.62 (1H, dd, J=12.4, 2.2 Hz), 7.77 (1H, S).

IR (KBr) cm⁻¹: 1653, 1610, 1519, 1437, 1291, 1283, 1267, 1138, 1114.

Mass m/z: 403 (M⁺).

Example 209 Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one 1) Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one

Following the procedure of Example 1 (6), 6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one and 4-chlorocinnamyl chloride were reacted to yield the title compound as a pale yellow crystalline powder (yield: 51.1%).

Melting point: 117-119° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.95 (3H, s), 3.98 (3H, s), 5.02 (2H, dd, J=6.8, 1.2 Hz), 6.43 (1H, dt, J=15.9, 6.8 Hz), 6.70 (1H, d, J=15.9 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.25 (2H, d, J=8.8 Hz), 7.31 (2H, d, J=8.8 Hz), 7.50 (1H, dt, J=8.5, 2.2 Hz), 7.62 (1H, dd, J=12.2, 2.2 Hz), 8.22 (1H, s).

IR (KBr) cm⁻¹: 1724, 1709, 1667, 1506, 1291, 1236, 1126, 831.

Mass m/z: 412 (M⁺), 414 (M⁺)

2) Preparation of 4-carboxy-2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (7), 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-methoxycarbonyl-2H-pyridazin-3-one was reacted to yield the title compound as a pale yellow crystalline powder (yield: 98.2%).

Melting point: 217.2-218.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.97 (3H, s), 5.10 (2H, d, J=6.8 Hz), 6.39 (1H, dt, J=15.9, 6.8 Hz), 6.75 (1H, d, J=15.9 Hz), 7.06 (1H, dd, J=8.5, 8.5 Hz), 7.30 (2H, d, J=8.5 Hz), 7.34 (2H, d, J=8.5 Hz), 7.57 (1H, m), 7.69 (1H, dd, J=12.2,. 2.2 Hz), 8.63 (1H, s), 13.99 (1H, s).

IR (KBr) cm⁻¹: 3059, 1744, 1629, 1523, 1480, 1438, 1426, 1296, 1272.

Mass m/z: 414 (M⁺), 416 (M⁺).

3) Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-carboxy-2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow crystals (yield: 17.0%).

Melting point: 158.2-160.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.95 (1H, t, J=5.9 Hz), 3.94 (3H, s), 4.73 (2H, dd, J=5.9, 1.2 Hz), 4.98 (2H, dd, J=6.6, 1.2 Hz), 6.40 (1H, dt, J=15.9, 6.6 Hz), 6.67 (1H, d, J=15.9 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.27 (2H, d, J=8.5 Hz), 7.32 (2H, d, J=8.5 Hz), 7.51 (1H, ddd, J=8.8, 2.2, 1.2 Hz), 7.63 (1H, dd, J=12.4, 2.2 Hz), 7.67 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 3392, 1648, 1603, 1523, 1440, 1284, 1273, 1140.

Mass m/z: 400 (M⁺), 402 (M⁺).

4) Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one was reacted to yield the title compound as pale yellow neeldes (yield: 90.7%).

Melting point: 135.8-136.4° C.

¹H NMR (400 MHz, CDCl₃) δ: 3.17 (3H, s), 3.95 (3H, s), 4.98 (2H, dd, J=6.6, 0.98 Hz), 5.28 (2H, d, J=1.5 Hz), 6.39 (1H, dt, J=15.9, 6.6 Hz), 6.67 (1H, d, J=15.9 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.27 (2H, d, J=8.5 Hz), 7.32 (2H, d, J=8.5 Hz), 7.50 (1H, m), 7.62 (1H, dd, J-12.2, 2.2 Hz), 7.77 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 1660, 1615, 1523, 1436, 1360, 1335, 1287, 1273, 1179.

Mass m/z: 478 (M⁺), 480 (M⁺)

5) Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-(4-methyl-1-piperazinyl)methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as pale brown neeldes (yield: 66.3%).

Melting point: 123.9-125.5° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.33 (3H, s), 2.52 (4H, brs), 2.62 (4H, brs), 3.58 (2H, d, J=1.2 Hz), 3.95 (3H, s), 4.98 (2H, dd, J=6.8, 1.2 Hz), 6.41 (1H, dt, J=15.9, 6.8 Hz), 6.66 (1H, d, J=15.9 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.26 (2H, d, J=8.5 Hz), 7.32 (2H, d, J=8.5 Hz), 7.53 (1H, ddd, J=8.5, 2.0, 1.2 Hz), 7.62 (1H, dd, J=12.4, 2.2 Hz), 7.75 (1H, t, J=1.2 Hz).

IR (KBr) cm⁻¹: 1647, 1606, 1522, 1439, 1282, 1270.

Mass m/z: 482 (M⁺), 484 (M⁺).

Example 210 Preparation of 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-[4-(2-hydroxyethyl)-1-piperazinyl]methyl-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-(4-chlorocinnamyl)-6-(3-fluoro-4-methoxyphenyl)-4-methanesulfonyloxymethyl-2H-pyridazin-3-one and 1-piperazineethanol were reacted to yield the title compound as slightly-yellow needles (yield: 65.1%).

Melting point: 133.1-134.9° C.

¹H NMR (400 MHz, CDCl₃) δ: 2.57-2.62 (11H, m), 3.58 (2H, d, J=1.2 Hz), 3.63 (2H, t, J=5.4 Hz), 3.94 (3H, s), 4.97 (2H, d, J=6.6 Hz), 6.41 (1H, dt, J=15.9, 6.6 Hz), 6.67 (1H, d, J=15.9 Hz), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.26 (2H, d, J=8.5 Hz), 7.32 (2H, d, J=8.5 Hz), 7.53 (1H, m), 7.61 (1H, dd, J=12.4, 2.2 Hz), 7.75 (1H, s).

IR (KBr) cm⁻¹: 3451, 1647, 1605, 1523, 1438, 1285, 1274, 1137.

Mass m/z: 478 (M⁺), 480 (M⁺).

Example 211 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-[3-(4-methyl-1-piperazinyl)propyl]-2H-pyridazin-3-one 1) Preparation of 4-bromomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

2-Cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one (185 mg, 0.61 mmol), carbon tetrabromide (404 mg, 1.2 mmol) and pyridine (48 mg, 0.61 mmol) were dissolved in tetrahydrofuran (3 mL), and under ice-cold stirring, a solution of triphenylphosphine (319 mg, 1.2 mmol) in tetrahydrofuran (3 mL) was added. Under ice cooling, the mixture was stirred for 1 hour, and further stirred overnight at room temperature. Insoluble materials were filtered off, the solvent was distilled off under reduced pressure, and the residue was isolated and purified by column chromatography on silica gel (hexane/ethyl acetate=2/1) to yield the title compound as a yellow powder (yield: 155 mg, 69.5%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.60 (4H, m), 1.58 (1H, m), 3.95 (3H, s), 4.12 (2H, d, J=7.3 Hz), 4.49 (2H, s), 7.03 (1H, dd, J=8.5, 8.5 Hz), 7.50 (1H, m), 7.60 (1H, dd, J=13.4, 2.2 Hz), 7.77 (1H, s).

2) Preparation of 2-cyclopropylmethyl-4-[2,2-di(tert-butoxycarbonyl)ethyl]-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

After 55% sodium hydride (322 mg, 7.38 mmol) was added to a solution of di-tert-butyl malonate (970 mg, 4.48 mmol) in N,N-dimethylformamide (10 mL), 4-bromomethyl-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one (1.8 g, 4.90 mmol) was added under ice-cold stirring. The reaction mixture was stirred at room temperature for 1 hour, poured into water, and extracted with ethyl acetate. The extract was washed with brine and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure. The residue was isolated and purified by column chromatography on silica gel (hexane/ethyl acetate=3/1) to yield the title compound as a yellow powder (yield: 1.39 mg, 61.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.50-0.58 (2H, m), 1.41 (18H, s), 1.56 (1H, m), 3.12 (2H, d, J=7.8 Hz), 3.87 (1H, t, J=7.8 Hz), 3.94 (3H, s), 4.0.9 (2H, d, J=7.8 Hz), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.43 (1H, d, J=8.5 Hz), 7.50 (1H, s), 7.57 (1H, dd, J=12.4, 2.2 Hz).

3) Preparation of 4-(2-carboxyethyl)-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Trifluoroacetic acid (21 mL) was added to 2-cyclopropylmethyl-4-[2,2-di(tert-butoxycarbonyl)ethyl]-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one (1.39 g, 2.77 mmol), and the mixture was stirred at room temperature for 30 minutes. The solvent was distilled off under reduced pressure, and toluene was added further, followed by azeotropic boiling. The residue was heated at 190 to 200° C. for 30 minutes under a nitrogen atmosphere to yield the title compound as a pale brown powder (yield: 907 mg, 94.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.45-0.50 (2H, m), 0.50-0.60 (2H, m), 1.41 (1H, m), 2.80 (2H, t, J=7.1 Hz), 2.97 (2H, t, J=7.1 Hz), 3.94 (3H, s), 4.10 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.47 (1H, d, J=8.5 Hz), 7.55 (1H, s), 7.59 (1H, dd, J=12.4, 2.2 Hz).

4) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-hydroxypropyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (8), 4-(2-carboxyethyl)-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a brown oil (yield: 82.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.52 (2H, m), 0.52-0.60 (2H, m), 1.42 (1H, m), 1.88-1.94 (2H, m), 2.81 (2H, t, J=6.1 Hz), 3.63 (2H, t, J=5.9 Hz), 3.95 (3H, s), 4.12 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.50 (1H, m), 7.52 (1H, s), 7.60 (1H, dd, J=12.4, 2.2 Hz).

5) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (9), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-hydroxypropyl)-2H-pyridazin-3-one was reacted to yield the title compound as a pale brown powder (yield: 82.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.51 (2H, m), 0.51-0.60 (2H, m), 1.41 (1H, m), 2.13-2.21 (2H, m), 2.80 (2H, t, J=7.1 Hz), 3.04 (3H, s), 3.94 (3H, s), 4.09 (2H, d, J=7.3 Hz), 4.31 (2H, t, J=6.1 Hz), 7.02 (1H, dd, J=8.5, 8.5 H z), 7.49 (1H, d, J=8.5 H z), 7.53 (1H, s), 7.61 (1H, dd, J=12.4, 2.2 Hz).

6) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-[3-(4-methyl-1-piperazinyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one and 1-methylpiperazine were reacted to yield the title compound as a yellow oil (yield: 62.0%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.50-0.60 (2H, m), 1.41 (1H, m), 1.90-2.00 (2H, m), 2.45 (3H, s), 2.50-3.00 (12H, m), 3.94 (3H, s), 4.08 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.48 (1H, s), 7.50 (1H, d, J=8.5Hz), 7.70 (1H, dd, J=12.3, 2.0 Hz).

IR (Neat) cm⁻¹: 1648, 1607, 1524, 1286, 1122, 1022, 755.

Mass m/z: 414 (M⁺).

Example 212 Preparation of 2-cyclopropylmethyl-4-(3-dimethylaminopropyl)-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 7, 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one and dimethylamine were reacted to yield the title compound as a yellow powder (yield: 64.7%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.53-0.60 (2H, m), 1.40 (1H, m), 2.24-2.35 (2H, m), 2.75-2.80 (2H, m), 2.79 (6H, s), 3.03 (2H, t, J=7.3 Hz), 3.94 (3H, s), 4.08 (2H, d, J=7.1 Hz), 7.04 (1H, dd, J=8.5, 8.5 Hz), 7.57 (1H, d, J=8.5 Hz), 7.65 (1H, dd, J=12.4, 2.2 Hz), 7.72 (1H, s).

IR (Neat) cm⁻¹: 1649, 1608, 1524, 1288, 1122, 1022, 761.

Mass m/z: 359 (M⁺).

Example 213 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-[3-(1-piperazinyl)propyl]-2H-pyridazin-3-one 1) Preparation of 2-cyclopropylmethyl-4-[3-(4-tert-butoxycarbonyl-1-piperazinyl)propyl]-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one and tert-butyl 1-piperazinecarboxylate were reacted to yield the title compound as a yellow oil (yield: 76.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.52-0.60 (2H, m), 1.44 (1H, m), 1.46 (9H, s), 2.00-2.40 (2H, m), 2.50-2.80 (6H, m), 3.50-3.75 (6H, m), 3.94 (3H, s), 4.08 (2H, d, J=7.1 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.47-7.65 (3H, m).

2) Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)4-[3-(1-piperazinyl)propyl]-2H-pyridazin-3-one

Following the procedure of Example 20, 2-cyclopropylmethyl-4-[3-(4-tert-butoxycarbonyl-1-piperazinyl)propyl]-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one was reacted to yield the title compound as a yellow oil (yield: 78.9%).

¹H NMR (400 MHz, CDCl₃) δ: 0.43-0.50 (2H, m), 0.50-0.59 (2H, m), 1.42 (1H, m), 1.82-1.92 (2H, m), 2.40-2.50 (6H, m), 2.68 (2H, t, J=7.6 Hz), 2.93-2.95 (4H, m), 3.94 (3H, s), 4.08 (2H, d, J=7.3 Hz), 5 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.45 (1H, s), 7.48 (1H, d, J=8.5 Hz), 7.59 (1H, dd, J=11.4, 2.0 Hz).

IR (Neat) cm⁻¹: 1648, 1607, 1523, 1288, 1122, 1023, 760.

Mass m/z: 400 (M⁺).

Example 214 Preparation of 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-[3-(1-piperazinyl)propyl]-2H-pyridazin-3-one dihydrochloride

Following the procedure of Example 4, 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-[3-(1-piperazinyl)propyl]-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 83.1%).

Melting point: 174-178° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.39-0.45 (2H, m), 0.45-0.55 (2H, m), 1.32 (1H, m), 2.00-2.25 (2H, m), 2.62-2.66 (2H, m), 3.20-3.85 (10H, m), 3.90 (3H, s), 4.01 (2H, d, J=7.1 Hz), 7.28 (1H, dd, J=8.8, 8.8 Hz), 7.72-7.80 (2H, m), 7.96 (1H, s).

IR (KBr) cm⁻¹: 1647, 1604, 1523, 1297, 1123, 1020, 762.

Example 215 Preparation of 4-[3-[N,N-bis(2-hydroxyethyl)amino]propyl]-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 1 (10), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one and diethanolamine were reacted to yield the title compound as a yellow oil (yield: 13.1%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.50-0.60 (2H, m), 1.41 (1H, m), 2.10-2.20 (2H, m), 2.76 (2H, t, J=7.3 Hz), 3.00-3.15 (6H, m), 3.87-3.92 (4H, m), 3.94 (3H, s), 4.08 (2H, d, J=7.3 Hz), 7.02 (1H, dd, J=8.5, 8.5 Hz), 7.53 (1H, d, J=8.5 Hz), 7.60 (1H, s), 7.62 (1H, dd, J=12.4, 2.2 Hz).

IR (Neat) cm⁻¹: 1645, 1602, 1524, 1288, 1123, 1024, 756.

Mass m/z: 400 (M⁺−CH₂OH).

Example 216 Preparation of 4-(3-aminopropyl)-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one

Following the procedure of Example 24 (1), 2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-4-(3-methanesulfonyloxypropyl)-2H-pyridazin-3-one was reacted to yield a crude product. Without purification, the crude product was reacted further in accordance with the procedure of Example 24 (2) to yield the title compound as a yellow oil (yield: 67.8%).

¹H NMR (400 MHz, CDCl₃) δ: 0.44-0.50 (2H, m), 0.50-0.60 (2H, m), 1.41 (1H, m), 1.84-1.96 (2H, m), 2.67-2.80 (4H, m), 2.87 (2H, t, J=6.1 Hz), 3.94 (3H, s), 4.08 (2H, d, J=7.3 Hz), 7.01 (1H, dd, J=8.5, 8.5 Hz), 7.49 (1H, d, J=8.5 Hz), 7.50 (1H, s), 7.59 (1H, dd, J=12.4, 2.2 Hz).

IR (Neat) cm⁻¹: 3370, 1648, 1606, 1523, 1289, 1122, 1023, 760.

Mass m/z: 331 (M⁺).

Example 217 Preparation of 4-(3-aminopropyl)-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl)-2H-pyridazin-3-one hydrochloride

Following the procedure of Example 4, 4-(3-aminopropyl)-2-cyclopropylmethyl-6-(3-fluoro-4-methoxyphenyl]-2H-pyridazin-3-one was reacted to yield the title compound as a slightly-yellow crystalline powder (yield: 70.6%).

Melting point: 183-185° C.

¹H NMR (400 MHz, DMSO-d₆) δ: 0.40-0.45 (2H, m), 0.45-0.55 (2H, m), 1.32 (1H, m), 1.88-1.93 (2H, m), 2.64 (2H, t, J=7.3 Hz), 2.78-2.88 (2H, m), 3.90 (3H, s), 4.00 (2H, d, J=7.3 Hz), 7.28 (1H, dd, J=8.5, 8.5 Hz), 7.70-7.78 (2H, m), 7.96 (1H, s).

IR (KBr) cm⁻¹: 3437, 1648, 1608, 1526, 1273, 1122, 1021, 762.

Experiment 1

Inhibitory Activity Against Interleukin-1β Production

HL-60 cells were cultured for 4 days until confluence on RPMI 1640 medium with 10% fetal bovine serum (FBS) added thereto. The medium was centrifuged. The supernatant was discarded, and the cells were then suspended at 1×10⁶ cells/mL on RPMI 1640 medium with 3% FBS, and lipopolysaccharide was added to give a final concentration of 10 pg/mL. The culture was inoculated at 1 mL/well to a 24-well plate. A sample compound was added at 1 μL/well, followed by culturing for 3 days. Three days later, the amount of interleukin-1β in each culture was determined by ELISA. Each IC₅₀ value was determined by a comparison in yield with a control to which no test sample was added. Results on some representative compounds are shown in Table 1. TABLE 1 (I)

Inhibitory activity against IL-1β Example production No. X Y Z n R¹ R²(R³)N— Salt IC50 (μM) 8 Me F H 1 iso-Bu Me₂N— HCl 3.45 14 MeO F H 1 CyprCH₂ Me₂N— HCl 3.61 18 MeO F H 1 CyprCH₂

2HCl 5.40 21 MeO F H 1 CyprCH₂

2HCl 1.01 23 MeO F H 1 CyprCH₂ (HOCH₂CH₂)₂N— HCl 0.33 25 MeO F H 1 CyprCH₂ H₂N— HCl 2.74 45 Me H H 1 iso-Bu Me₂N— HCl 6.21 47 Me H H 1 iso-Bu Et₂N— HCl 5.20 49 Me H H 1 iso-Bu (HOCH₂CH₂)₂N— HCl 3.53 83 F Me H 1 iso-Bu

2HCl 0.27 89 F Me H 1 iso-Bu Me₂N— HCl 5.50 108 F F H 1 iso-Bu (HOCH₂CH₂)₂N— HCl 3.44 143 F Me H 1

2HCl 8.55 149 MeS H H 1 CyprCH₂

2HCl 1.63 153 MeS H H 1 CyprCH₂ Me₂N— HCl 0.58 161 MeS H H 1 iso-Bu Me₂N— HCl 2.78 163 MeS H H 1 iso-Bu

HCl 2.78 213 MeO F H 3 CyprCH₂

free 0.24 216 MeO F H 3 CyprCH₂ H₂N— free 1.14 189 MeO F H 1

free 0.87 192 MeO F H 1

free 0.64 CyprCH₂: Cyclopropylmethyl

Experiment 2 Water Solubility Test

Testing method

Each sample compound was weighed in the amount shown in Table 2, to which purified water was added in 0.05 mL aliquots. The solubility (%) of the compound was determined based on the amount of water required for its dissolution.

Results

As is shown in Table 2, the compounds of the present invention showed water solubility significantly improved over the comparative compounds. TABLE 2 Amount of Weighed amount added water Example No. (mg) (mL) Solubility (%)  14 2.048 0.25 0.8  18 1.048 0.1  1  21 10.47 0.05 >20  23 10.82 0.1  10  25 1.025 0.25 0.4  45 10.37 0.25 4  47 10.47 0.05 >20  89 10.57 0.05 >20 108 9.75  0.045 >20 149 3.09 0.03 >10 153 2.95 0.6  0.5 214 5.061 0.05 10 193 5.032 0.1  5 217 5.061 0.05 10 195 5.072 2.2  0.2 188 2.008 2.5  0.08 206 2.042 3.5  0.06 Comparative 0.677 100    <0.001 Compound 1 (insoluble) Comparative 0.742 100    <0.001 Compound 2 (insoluble) Comparative 0.740 100    <0.001 Compound 3 (insoluble) Comparative 0.95 100    <0.001 Compound 4 (insoluble)

Comp. comp'd 1

Comp. comp'd 2

Comp. comp'd 3

Comp. comp'd 4

Experiment 3 Oral Absorbability Test on Rats

The compound of Example 83 and the comparative compound 3 were suspended at 2 mg/mL with a 0.5% MC solution in mortars, respectively, and were orally administered to male SD rats at 10 mg/5 mL/kg. Upon elapsed time of 0.25, 0.5, 1, 2, 4, 6 and 8 hours after the administration, blood samples were collected and then centrifuged to provide plasma samples. The plasma levels of the respective compounds were determined by HPLC. As is shown in FIG. 1, no substantial absorption was observed on the comparative compound 3, but good absorption was observed on the compound of Example 83 equipped with increased water solubility. The compound of Example 83 is, therefore, useful as an orally dosable medicine.

Experiment 4 Oral Absorbability Test on Rats and Mice

In a similar manner as in Experiment 3, test compounds of Examples 23, 25 and 143 were orally administered to mice and rats to test their oral absorbability. As is shown in FIGS. 2 to 4, good absorbability was observed on the compounds of Examples 23, 25 and 143 so that they are useful as orally dosable medicines.

Having described the present invention, it will now be apparent to one of ordinary skill in the art that many changes and modifications may be made to the above-described embodiments without departing from the spirit and the scope of the present invention. 

1. A phenylpyridazine compound having the formula (1):

wherein: R¹ is a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkenyl group; R² and R³ each independently represents a hydrogen atom or an alkyl, hydroxyalkyl, dihydroxyalkyl or alkynyl group, or R² and R³ are fused together with the adjacent nitrogen atom to form a substituted or unsubstituted, saturated heterocyclic group having as heterocyclic ring atoms C and N or having as heterocyclic ring atoms C, N and O; X, Y and Z each independently represents a hydrogen or halogen atom, a substituted or unsubstituted alkyl, alkoxy, alkylthio, alkylsulfinyl or alkylsulfonyl group, or a substituted or unsubstituted aryl group; and n stands for a number of from 1 to 5; with the proviso that R² and R³ are not hydrogen atoms or the same C₁-C₃ alkyl groups at the same time when R¹ is a benzyl group or a C₁-C₃ alkyl group; or a salt thereof
 2. The compound of claim 1, wherein R¹ is substituted or unsubstituted alkyl having 1 to 7 carbon atoms or substituted or unsubstituted alkenyl having 2 to 7 carbon atoms.
 3. The compound of claim 2, wherein one or more substituents on said alkyl or alkenyl group represented by R¹ are each independently an aryl group having 6 to 14 carbon atoms or a 5- or 6-membered heteroaryl group having 1 to 3 nitrogen atoms; and said aryl or heteroaryl group are each unsubstituted or substituted by 1 to 3 substituents selected from the group consisting of halogen atoms, alkyl groups and alkoxy groups.
 4. The compound of claim 1, wherein R² and R³ each independently represents hydrogen, alkyl, hydroxyalkyl, dihydroxyalkyl or alkynyl; or R² and R³ are fused together with the adjacent nitrogen atom to form a 5- or 7-membered, nitrogen-containing, saturated heterocyclic group, said heterocyclic group being unsubstituted or substituted with one or more halogen atoms, or alkyl, alkoxycarbonyl or aralkyl groups.
 5. The compound of claim 1, wherein X, Y and Z each independently are hydrogen, halogen, alkyl which is unsubstituted or substituted by one or more halogen atoms, alkoxy, alkylthio, alkylsulfinyl, alkylsulfonyl, or C₆-C₁₄ aryl groups which are unsubstituted or substituted by one or more of halogen, alkyl and alkoxy.
 6. The compound of claim 1, wherein R¹ is isobutyl, cyclopropylmethyl, cyclopentylmethyl, cinnamyl, halogenocinnamyl, benzyl, halogenobenzyl, dihalogenobenzyl or (halogenophenyl)propyl; R² and R³ are each independently hydrogen, C₁₋₇ alkyl, C₁₋₇ hydroxyalkyl or propargyl; said heterocyclic group formed by R² and R³ is substituted with C₁₋₇ alkyl or is piperazinyl, piperidino, pyrrolidino or morpholino which is unsubstituted or substituted by one or more benzyl; X is methyl, methoxy, methylthio or halogen; Y is hydrogen or halogen; Z is hydrogen; and n is 1 or
 3. 7. (canceled)
 8. A pharmaceutical composition comprising at least one of the phenylpyridazine compound, or a salt thereof, of claim 1, and a pharmaceutically-acceptable carrier.
 9. A method of using a phenylpyridazine compound, or a salt thereof, the method comprising inhibiting interleukin-1β production in a mammal by administering at least one of the phenylpyridazine compound, or a salt thereof, of claim 1 to the mammal.
 10. (canceled)
 11. The method of claim 9, wherein the administering prevents or treats rheumatism in the mammal.
 12. The method of claim 9, wherein the administering prevents or treats arthritis in the mammal.
 13. (canceled)
 14. The method of claim 9, wherein the mammal is a human.
 15. The method of claim 9, wherein the administering is by oral administration.
 16. The method of claim 9, wherein the administering is by parenteral administration.
 17. A The pharmaceutical composition of claim 8, wherein the pharmaceutical composition is in a form suitable for oral administration.
 18. The pharmaceutical composition of claim 17, wherein the form suitable for oral administration is a tablet. 